Linear combination codebook for csi reporting in advanced wireless communication systems

ABSTRACT

A method of a user equipment (UE) for a channel state information (CSI) feedback in an advanced communication system. The method comprises receiving, from a base station (BS), CSI feedback configuration information for a pre-coding matrix indicator (PMI) feedback based on a linear combination (LC) codebook, wherein the PMI comprises a first PMI (i1) and a second PMI (i2), determining the first PMI (i1) and the second PMI (i2) indicating an LC pre-coder that corresponds to a weighted linear combination of a first beam and a second beam, wherein the first PMI (i1) includes a first beam indicator (i1,1, i1,2) and a second beam indicator (i1,3) that indicate the first beam and a distance (d1, d2) of the second beam in accordance with the first beam, respectively; and the second PMI (i2) indicates weights assigned to the first beam and the second beam. The method further comprises transmitting, to the BS, the CSI feedback over an uplink channel including the determined first PMI (i1) and the second PMI (i2).

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 15/650,715, filed on Jul. 14, 2017, which claims priority toU.S. Provisional Patent Application No. 62/367,184, filed on Jul. 27,2016, U.S. Provisional Patent Application No. 62/371,663, filed on Aug.5, 2016, U.S. Provisional Patent Application No. 62/380,794, filed onAug. 29, 2016, U.S. Provisional Patent Application No. 62/397,103, filedon Sep. 20, 2016, U.S. Provisional Patent Application No. 62/410,917,filed on Oct. 21, 2016, U.S. Provisional Patent Application No.62/417,797, filed on Nov. 4, 2016, U.S. Provisional Patent ApplicationNo. 62/420,412, filed on Nov. 10, 2016, U.S. Provisional PatentApplication No. 62/423,234, filed on Nov. 17, 2016, and U.S. ProvisionalPatent Application No. 62/463,815, filed on Feb. 27, 2017. The contentof the above-identified patent documents are incorporated herein byreference.

TECHNICAL FIELD

The present application relates generally to channel state information(CSI) reporting operation in advanced wireless communication systems.More specifically, this disclosure relates to linear combinationprecoding matrix indicator (PMI) codebook for CSI reporting.

BACKGROUND

Understanding and correctly estimating the channel in an advancewireless communication system between a user equipment (UE) and an eNodeB (eNB) is important for efficient and effective wireless communication.In order to correctly estimate the channel conditions, the UE may report(e.g., feedback) information about channel measurement, e.g., CSI, tothe eNB. With this information about the channel, the eNB is able toselect appropriate communication parameters to efficiently andeffectively perform wireless data communication with the UE. However,with increase in the numbers of antennas and channel paths of wirelesscommunication devices, so too has the amount of feedback increased thatmay be needed to ideally estimate the channel. This additionally-desiredchannel feedback may create additional overheads, thus reducing theefficiency of the wireless communication, for example, decrease the datarate.

SUMMARY

The present disclosure relates to a pre-5^(th)-generation (5G) or 5Gcommunication system to be provided for supporting higher data ratesbeyond 4^(th)-generation (4G) communication system such as long termevolution (LTE). Embodiments of the present disclosure provide anadvanced CSI reporting based on a linear combination codebook for MIMOwireless communication systems.

In one embodiment, a user equipment (UE) for a channel state information(CSI) feedback in an advanced communication system is provided. The UEcomprises a transceiver configured to receive, from a base station (BS),CSI feedback configuration information for a pre-coding matrix indicator(PMI) feedback based on a linear combination (LC) codebook, wherein thePMI comprises a first PMI (i₁) and a second PMI (i₂). The UE furthercomprises at least one processor configured to determine the first PMI(i₁) and the second PMI (i₂) indicating an LC pre-coder that correspondsto a weighted linear combination of a first beam and a second beam. Thefirst PMI (i₁) includes a first beam indicator (i_(1,1), i_(1,2)) and asecond beam indicator (i_(1,3)) that indicate the first beam and adistance (d₁, d₂) of the second beam in accordance with the first beam,respectively, and the second PMI (i₂) indicates weights assigned to thefirst beam and the second beam. The UE further comprises the transceiverconfigured to transmit, to the BS, the CSI feedback over an uplinkchannel including the first PMI (i₁) and the second PMI (i₂).

In another embodiment, a base station (BS) for a channel stateinformation (CSI) feedback in an advanced communication system isprovided. The BS comprises a transceiver configured to transmit, to auser equipment (UE), CSI feedback configuration information for apre-coding matrix indicator (PMI) feedback based on a linear combination(LC) codebook, wherein the PMI comprises a first PMI (i₁) and a secondPMI (i₂). The first PMI (i₁) and the second PMI (i₂) indicate an LCpre-coder that corresponds to a weighted linear combination of a firstbeam and a second beam, the first PMI (i₁) includes a first beamindicator (i_(1,1), i_(1,2)) and a second beam indicator (i_(1,3)) thatindicate the first beam and a distance (d₁, d₂) of the second beam inaccordance with the first beam, respectively, and the second PMI (i₂)indicates weights assigned to the first beam and the second beam. The BSfurther comprises the transceiver configured to receive, from the UE,the CSI feedback over an uplink channel including the first PMI (i₁) andthe second PMI (i₂).

In yet another embodiment, a method of a user equipment (UE) for achannel state information (CSI) feedback in an advanced communicationsystem is provided. The method comprises receiving, from a base station(BS), CSI feedback configuration information for a pre-coding matrixindicator (PMI) feedback based on a linear combination (LC) codebook,wherein the PMI comprises a first PMI (i₁) and a second PMI (i₂),determining the first PMI (i₁) and the second PMI (i₂) indicating an LCpre-coder that corresponds to a weighted linear combination of a firstbeam and a second beam. The first PMI (i₁) includes a first beamindicator (i_(1,1), i_(1,2)) and a second beam indicator (i_(1,3)) thatindicate the first beam and a distance (d₁, d₂) of the second beam inaccordance with the first beam, respectively, and the second PMI (i₂)indicates weights assigned to the first beam and the second beam. Themethod further comprises transmitting, to the BS, the CSI feedback overan uplink channel including the determined first PMI (i₁) and the secondPMI (i₂).

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

Aspects, features, and advantages of the present disclosure are readilyapparent from the following detailed description, simply by illustratinga number of particular embodiments and implementations, including thebest mode contemplated for carrying out the present disclosure. Thepresent disclosure is also capable of other and different embodiments,and its several details can be modified in various obvious respects, allwithout departing from the spirit and scope of the present disclosure.Accordingly, the drawings and description are to be regarded asillustrative in nature, and not as restrictive. The present disclosureis illustrated by way of example, and not by way of limitation, in thefigures of the accompanying drawings.

In the following, for brevity, both FDD and TDD are considered as theduplex method for both DL and UL signaling.

Although exemplary descriptions and embodiments to follow assumeorthogonal frequency division multiplexing (OFDM) or orthogonalfrequency division multiple access (OFDMA), disclosure can be extendedto other OFDM-based transmission waveforms or multiple access schemessuch as filtered OFDM (F-OFDM).

This present disclosure covers several components which can be used inconjunction or in combination with one another, or can operate asstandalone schemes.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure;

FIG. 2 illustrates an example eNodeB (eNB) according to embodiments ofthe present disclosure;

FIG. 3 illustrates an example user equipment (UE) according toembodiments of the present disclosure;

FIG. 4A illustrates a high-level diagram of an orthogonal frequencydivision multiple access transmit path according to embodiments of thepresent disclosure;

FIG. 4B illustrates a high-level diagram of an orthogonal frequencydivision multiple access receive path according to embodiments of thepresent disclosure;

FIG. 5 illustrates an example structure for a downlink (DL) subframeaccording to embodiments of the present disclosure;

FIG. 6 illustrates an example transmission structure of an uplink (UL)subframe according to embodiments of the present disclosure;

FIG. 7 illustrates an example transmitter block diagram for a physicaldownlink shared channel (PDSCH) subframe according to embodiments of thepresent disclosure;

FIG. 8 illustrates an example receiver block diagram for a PDSCHsubframe according to embodiments of the present disclosure;

FIG. 9 illustrates an example transmitter block diagram for a physicaluplink shared channel (PUSCH) subframe according to embodiments of thepresent disclosure;

FIG. 10 illustrates an example receiver block diagram for a physicaluplink shared channel (PUSCH) in a subframe according to embodiments ofthe present disclosure;

FIG. 11 illustrates an example configuration of a two dimensional (2D)array according to embodiments of the present disclosure;

FIG. 12 illustrates an example dual-polarized antenna port layouts for{2, 4, 8, 12, 16} ports according to embodiments of the presentdisclosure;

FIG. 13 illustrates an example dual-polarized antenna port layouts for{20, 24, 28, 32} ports according to embodiments of the presentdisclosure;

FIG. 14 illustrates an example linear combination pre-coding matrixindicator (PMI) pre-coder (L=4) according to embodiments of the presentdisclosure;

FIG. 15 illustrates an example periodic channel state information (CSI)reporting using a linear combination codebook according to embodimentsof the present disclosure;

FIG. 16 illustrates an example W1 codebook according to embodiments ofthe present disclosure;

FIG. 17 illustrates example master beam groups according to embodimentsof the present disclosure;

FIG. 18 illustrates an example beam selection according to embodimentsof the present disclosure;

FIG. 19 illustrates an example class A W1 beam groups for rank 1-8 andcodebook-configuration 2, 3, and 4 according to embodiments of thepresent disclosure;

FIG. 20 illustrates an example non-orthogonal and orthogonal master beamgroups 1D port layouts (N₁>1, N₂=1) according to embodiments of thepresent disclosure;

FIG. 21 illustrates example non-orthogonal and orthogonal master beamgroups of 2D port layouts (N1>1, N2>1) according to embodiments of thepresent disclosure;

FIG. 22 illustrates example non-orthogonal and orthogonal master beamgroups with (L₁, L₂)=(4, 2) for N₁≥N₂ according to embodiments of thepresent disclosure;

FIG. 23 illustrates an example beam selection from a non-orthogonalmaster beam group with (L1, L2)=(8, 1) for 1D layouts according toembodiments of the present disclosure;

FIG. 24 illustrates an example beam selection from a non-orthogonalmaster beam group with (L1, L2)=(4, 2) for 2D layouts according toembodiments of the present disclosure;

FIG. 25 illustrates an example beam selection from an orthogonal masterbeam group with (L1, L2)=(8, 1) for 1D layouts according to embodimentsof the present disclosure;

FIG. 26 illustrates an example beam selection from an orthogonal masterbeam group with (L₁, L₂)=(4, 2) for 2D layouts according to embodimentsof the present disclosure;

FIG. 27 illustrates an example LC codebook CB4-2 according toembodiments of the present disclosure;

FIG. 28 illustrates an example LC codebook CB5 according to embodimentsof the present disclosure;

FIG. 29 illustrates a table for a Codebook-Config parameter to rank 1beam grouping mapping according to embodiments of the presentdisclosure;

FIG. 30 illustrates a table for BGI or BI to beam group mapping for anLC codebook according to embodiments of the present disclosure;

FIG. 31 illustrates a table for a basis for an LC codebook CB1 accordingto embodiments of the present disclosure; and

FIG. 32 illustrates a table for a basis for a LC W1 codebook CB2according to embodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 through FIG. 28, discussed below, and the various embodimentsused to describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artmay understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The following documents and standards descriptions are herebyincorporated by reference into the present disclosure as if fully setforth herein: 3GPP TS 36.211 v13.0.0, “E-UTRA, Physical channels andmodulation” (REF1); 3GPP TS 36.212 v13.0.0, “E-UTRA, Multiplexing andChannel coding” (REF2); 3GPP TS 36.213 v13.0.0, “E-UTRA, Physical LayerProcedures” (REF3); 3GPP TS 36.321 v13.0.0, “E-UTRA, Medium AccessControl (MAC) protocol specification” (REF4); 3GPP TS 36.331 v13.0.0,“E-UTRA, Radio Resource Control (RRC) protocol specification” (REF5);and RP-160623, “New WID Proposal: Enhancements on Full-Dimension (FD)MIMO for LTE,” Samsung.

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a “beyond 4G network” or a“post LTE system.”

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission coverage, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques and the like arediscussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul communication, moving network,cooperative communication, coordinated multi-points (CoMP) transmissionand reception, interference mitigation and cancellation and the like.

In the 5G system, hybrid frequency shift keying and quadrature amplitudemodulation (FQAM) and sliding window superposition coding (SWSC) as anadaptive modulation and coding (AMC) technique, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

FIGS. 1-4B below describe various embodiments implemented in wirelesscommunications systems and with the use of OFDM or OFDMA communicationtechniques. The descriptions of FIGS. 1-3 are not meant to implyphysical or architectural limitations to the manner in which differentembodiments may be implemented. Different embodiments of the presentdisclosure may be implemented in any suitably-arranged communicationssystem.

FIG. 1 illustrates an example wireless network 100 according toembodiments of the present disclosure. The embodiment of the wirelessnetwork 100 shown in FIG. 1 is for illustration only. Other embodimentsof the wireless network 100 could be used without departing from thescope of this disclosure.

As shown in FIG. 1, the wireless network 100 includes an eNB 101, an eNB102, and an eNB 103. The eNB 101 communicates with the eNB 102 and theeNB 103. The eNB 101 also communicates with at least one network 130,such as the Internet, a proprietary Internet Protocol (IP) network, orother data network.

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business (SB); a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); aUE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M), such as a cell phone, a wireless laptop, a wirelessPDA, or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 maycommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, WiFi, or other wireless communication techniques.

Depending on the network type, the term “base station” or “BS” can referto any component (or collection of components) configured to providewireless access to a network, such as transmit point (TP),transmit-receive point (TRP), an enhanced base station (eNodeB or eNB),gNB, a macrocell, a femtocell, a WiFi access point (AP), or otherwirelessly enabled devices. Base stations may provide wireless access inaccordance with one or more wireless communication protocols, e.g., 5G3GPP New Radio Interface/Access (NR), long term evolution (LTE), LTEadvanced (LTE-A), High Speed Packet Access (HSPA), Wi-Fi802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “eNodeB”and “eNB” are used in this patent document to refer to networkinfrastructure components that provide wireless access to remoteterminals. Also, depending on the network type, other well-known termsmay be used instead of “user equipment” or “UE,” such as “mobilestation,” “subscriber station,” “remote terminal,” “wireless terminal,”or “user device.” For the sake of convenience, the terms “userequipment” and “UE” are used in this patent document to refer to remotewireless equipment that wirelessly accesses an eNB, whether the UE is amobile device (such as a mobile telephone or smartphone) or is normallyconsidered a stationary device (such as a desktop computer or vendingmachine).

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of the UEs 111-116include circuitry, programming, or a combination thereof, for efficientCSI reporting on PUCCH in an advanced wireless communication system. Incertain embodiments, and one or more of the eNBs 101-103 includescircuitry, programming, or a combination thereof, for receivingefficient CSI reporting on uplink channel in an advanced wirelesscommunication system.

Although FIG. 1 illustrates one example of a wireless network 100,various changes may be made to FIG. 1. For example, the wireless network100 could include any number of eNBs and any number of UEs in anysuitable arrangement. Also, the eNB 101 could communicate directly withany number of UEs and provide those UEs with wireless broadband accessto the network 130. Similarly, each eNB 102-103 could communicatedirectly with the network 130 and provide UEs with direct wirelessbroadband access to the network 130. Further, the eNBs 101, 102, and/or103 could provide access to other or additional external networks, suchas external telephone networks or other types of data networks.

FIG. 2 illustrates an example eNB 102 according to embodiments of thepresent disclosure. The embodiment of the eNB 102 illustrated in FIG. 2is for illustration only, and the eNBs 101 and 103 of FIG. 1 could havethe same or similar configuration. However, eNBs come in a wide varietyof configurations, and FIG. 2 does not limit the scope of thisdisclosure to any particular implementation of an eNB.

As shown in FIG. 2, the eNB 102 includes multiple antennas 205 a-205 n,multiple RF transceivers 210 a-210 n, transmit (TX) processing circuitry215, and receive (RX) processing circuitry 220. The eNB 102 alsoincludes a controller/processor 225, a memory 230, and a backhaul ornetwork interface 235.

The RF transceivers 210 a-210 n receive, from the antennas 205 a-205 n,incoming RF signals, such as signals transmitted by UEs in the network100. The RF transceivers 210 a-210 n down-convert the incoming RFsignals to generate IF or baseband signals. The IF or baseband signalsare sent to the RX processing circuitry 220, which generates processedbaseband signals by filtering, decoding, and/or digitizing the basebandor IF signals. The RX processing circuitry 220 transmits the processedbaseband signals to the controller/processor 225 for further processing.

In some embodiments, the RF transceivers 210 a-210 n are capable oftransmitting, to a user equipment (UE), CSI feedback configurationinformation for a pre-coding matrix indicator (PMI) feedback based on alinear combination (LC) codebook, wherein the PMI comprises a first PMI(i₁) and a second PMI (i₂), wherein the first PMI (i₁) and the secondPMI (i₂) indicate an LC pre-coder that corresponds to a weighted linearcombination of a first beam and a second beam, the first PMI (i₁)includes a first beam indicator (i_(1,1), i_(1,2)) and a second beamindicator (i_(1,3)) that indicate the first beam and a distance (d₁, d₂)of the second beam in accordance with the first beam, respectively, andthe second PMI (i₂) indicates weights assigned to the first beam and thesecond beam.

In some embodiments, the RF transceivers 210 a-210 n are capable ofreceiving, from the UE, the CSI feedback over an uplink channelincluding the first PMI (i₁) and the second PMI (i₂).

In such embodiments, the first PMI (i₁) includes a relative powerindicator (RPI) (I_(p)) indicating a power of a weight assigned to thesecond beam relative to a power of a weight assigned to the first beam,and wherein the power of the weight assigned to the first beam is set to1 and the power of the weight assigned to the second beam is set to avalue among {0, √{square root over (¼)}, √{square root over (½)}, 1},and wherein a (i_(1,1)) and a (i_(1,2)) indicate an index of the firstbeam in a first dimension and a second dimension, respectively, and a(d₁) and a (d₂) indicate a distance of the second beam from the firstbeam in the first dimension and the second dimension, respectively.

In such embodiments, the first beam and the second beam correspond totwo discrete Fourier transform (DFT) beams selected from an oversampledDFT codebook comprising DFT beams:

${v_{l_{1},l_{2}} = \begin{bmatrix}u_{l_{2}} & {e^{j\frac{2\pi \; l_{1}}{O_{1}N_{1}}}u_{l_{2}}} & \ldots & {e^{j\frac{2\pi \; {l_{1}{({N_{1} - 1})}}}{O_{1}N_{1}}}u_{l_{2}}}\end{bmatrix}^{T}},{{u_{l_{2}} = {{1{\mspace{11mu} \;}{if}\mspace{14mu} N_{2}} = 1}};{u_{l_{2}} = \begin{bmatrix}1 & e^{j\frac{2\pi \; l_{2}}{O_{2}N_{2}}} & \ldots & e^{j\frac{2\pi \; {l_{2}{({N_{2} - 1})}}}{O_{2}N_{2}}}\end{bmatrix}}}$

otherwise, 0≤l₁≤O₁N₁−1, and 0≤l₂≤O₂N₂−1, where N₁ and N₂ indicate afirst and a second number of antenna ports in the first and the seconddimensions, respectively, and O₁ and O₂ indicate a first and a secondoversampling factors in the first and second dimensions, respectively.

In such embodiments, the distance (d₁, d₂) of the second beam relativeto a first beam index (k₁ ⁽⁰⁾, k₂ ⁽⁰⁾) indicated by the first beamindicator (i_(1,1), i_(1,2)) is such that the (d₁) belongs to a set ofintegers {0, 1, . . . , L₁−1} and the (d₂) belongs to a set of integers{0, 1, . . . , L₂−1}, respectively, wherein a beam group size (L₁, L₂)is determined by: N₁≥N₂>1: L₁=min(N₁,4), L₂=2; N₂>N₁>1: L₂=min(N₂,4),L₁=2; and N₂=1: L_(t)=min(N₁,8), L₂=1.

In such embodiments, a second beam index (k₁ ⁽¹⁾, k₂ ⁽¹⁾) is determinedby: k₁ ⁽¹⁾=k₁ ⁽⁰⁾+O₁d₁, k₂ ⁽¹⁾=k₂ ⁽⁰⁾+O₂d₂, where the (d₁, d₂) is suchthat the (d₁) belongs to a set of integers {0, 1, . . . , min(N₁,L₁)−1},the (d₂) belongs to a set of integers {0, 1, . . . , min(N₂,L₂)−1}, and(d₁,d₂)≠(0, 0).

In such embodiments, the second beam indicator (i_(1,3)) and thedistance (d₁, d₂) of the second beam are mapped based on a table givenby:

N₁ ≥ N₂, N₂ > N₁, N₁ ≥ 4, N₁ = 3, N₁ = 2, N₂ ≥ 4, N₂ = 3, N₁ ≥ 8 N₁ = 2,N₁ = 4, Value of N₂ ≠ 1 N₂ = 2 N₂ = 2 N₁ ≠ 1 N₁ = 2 N₂ = 1 N₂ = 1 N₂ = 1i_(1, 3) d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ 0 1 0 1 0 1 0 01 0 1 1 0 1 0 1 0 1 2 0 2 0 0 1 0 2 0 2 2 0 2 0 2 3 0 0 1 1 1 0 3 1 0 30 3 0 3 0 1 1 1 1 0 1 1 4 0 4 1 1 2 1 1 1 1 2 5 0 5 2 1 1 2 6 0 6 3 1 13 7 0

In some embodiments, the RF transceivers 210 a-210 n are capable ofreceiving a single wideband (WB) bit stream that indicates threecomponents jointly, the (i_(1,1), i_(1,2)) indicating the first beam,the (i_(1,3)) indicating the distance (d₁, d₂) of the second beam fromthe first beam, and the (I_(p)) indicating the power of the weightassigned to the second beam.

In some embodiments, the RF transceivers 210 a-210 n are capable ofreceiving multiple WB bit streams that indicate three componentsseparately, a first bit stream for the (i_(1,1), i_(1,2)) indicating thefirst beam, and either a second bit stream jointly indicating the(i_(1,3)) and the (I_(p)) for the second beam or a second bit stream anda third bit stream separately indicating the (i_(1,3)) and the (I_(p))for the second beam, respectively.

The TX processing circuitry 215 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 225. The TX processing circuitry 215 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 210 a-210 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 215 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 205 a-205 n.

The controller/processor 225 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 225 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 210 a-210 n, the RX processing circuitry 220, andthe TX processing circuitry 215 in accordance with well-knownprinciples. The controller/processor 225 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 225 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 205 a-205 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 225. In some embodiments, the controller/processor225 includes at least one microprocessor or microcontroller. Asdescribed in more detail below, the eNB 102 may include circuitry,programming, or a combination thereof for processing of CSI reporting onan uplink channel. For example, controller/processor 225 can beconfigured to execute one or more instructions, stored in memory 230,that are configured to cause the controller/processor to process vectorquantized feedback components such as channel coefficients.

The controller/processor 225 is also capable of executing programs andother processes resident in the memory 230, such as an OS. Thecontroller/processor 225 can move data into or out of the memory 230 asrequired by an executing process.

The controller/processor 225 is also coupled to the backhaul or networkinterface 235. The backhaul or network interface 235 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 235 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 235 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 235 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 235 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 230 is coupled to the controller/processor 225. Part of thememory 230 could include a RAM, and another part of the memory 230 couldinclude a Flash memory or other ROM.

Although FIG. 2 illustrates one example of eNB 102, various changes maybe made to FIG. 2. For example, the eNB 102 could include any number ofeach component shown in FIG. 2. As a particular example, an access pointcould include a number of interfaces 235, and the controller/processor225 could support routing functions to route data between differentnetwork addresses. As another particular example, while shown asincluding a single instance of TX processing circuitry 215 and a singleinstance of RX processing circuitry 220, the eNB 102 could includemultiple instances of each (such as one per RF transceiver). Also,various components in FIG. 2 could be combined, further subdivided, oromitted and additional components could be added according to particularneeds.

FIG. 3 illustrates an example UE 116 according to embodiments of thepresent disclosure. The embodiment of the UE 116 illustrated in FIG. 3is for illustration only, and the UEs 111-115 of FIG. 1 could have thesame or similar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 3, the UE 116 includes an antenna 305, a radiofrequency (RF) transceiver 310, TX processing circuitry 315, amicrophone 320, and receive (RX) processing circuitry 325. The UE 116also includes a speaker 330, a processor 340, an input/output (I/O)interface (IF) 345, a touchscreen 350, a display 355, and a memory 360.The memory 360 includes an operating system (OS) 361 and one or moreapplications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

In some embodiments, the RF transceiver 310 is capable of receiving,from a base station (BS), CSI feedback configuration information for apre-coding matrix indicator (PMI) feedback based on a linear combination(LC) codebook, wherein the PMI comprises a first PMI (i₁) and a secondPMI (i₂).

In some embodiments, the RF transceiver 310 is capable of transmitting,to the BS, the CSI feedback over an uplink channel including the firstPMI (i₁) and the second PMI (i₂).

In such embodiments, the first PMI (i₁) includes a relative powerindicator (RPI) (I_(p)) indicating a power of a weight assigned to thesecond beam relative to a power of a weight assigned to the first beam,and wherein the power of the weight assigned to the first beam is set to1 and the power of the weight assigned to the second beam is set to avalue among {0, √{square root over (¼)}, √{square root over (½)}, 1}.

In such embodiments, the first beam and the second beam correspond totwo discrete Fourier transform (DFT) beams selected from an oversampledDFT codebook comprising DFT beams:

${v_{l_{1},l_{2}} = \begin{bmatrix}u_{l_{2}} & {e^{j\frac{2\pi \; l_{1}}{O_{1}N_{1}}}u_{l_{2}}} & \ldots & {e^{j\frac{2\pi \; {l_{1}{({N_{1} - 1})}}}{O_{1}N_{1}}}u_{l_{2}}}\end{bmatrix}^{T}},{{u_{l_{2}} = {{1{\mspace{11mu} \;}{if}\mspace{14mu} N_{2}} = 1}};{u_{l_{2}} = \begin{bmatrix}1 & e^{j\frac{2\pi \; l_{2}}{O_{2}N_{2}}} & \ldots & e^{j\frac{2\pi \; {l_{2}{({N_{2} - 1})}}}{O_{2}N_{2}}}\end{bmatrix}}}$

otherwise, 0≤l₁≤0₁N₁−1, and 0≤l₂≤O₂N₂−1, where N₁ and N₂ indicate afirst and second number of antenna ports in the first and the seconddimensions, respectively, and O₁ and O₂ indicate a first and a secondoversampling factors in the first and second dimensions, respectively.

In such embodiments, the distance (d₁, d₂) of the second beam relativeto a first beam index (k₁ ⁽⁰⁾), k₂ ⁽⁰⁾) indicated by the first beamindicator (i_(1,1), i_(1,2)) is such that the (d₁) belongs to a set ofintegers {0, 1, . . . , L₁−1} and the (d₂) belongs to a set of integers{0, 1, . . . , L₂−1}, respectively.

In such embodiments, a beam group size (L₁, L₂) is determined by:N₁≥N₂>1: L₁=min(N₁,4), L₂=2; N₂>N₁>1: L₂=min(N₂,4), L₁=2; and N₂=1:L_(t)=min(N₁,8), L₂=1.

In such embodiments, a second beam index (k₁ ⁽¹⁾, k₂ ⁽¹⁾) is determinedby: k₁ ⁽¹⁾=k₁ ⁽⁰⁾+O₁d₁, k₂ ⁽¹⁾=k₂ ⁽⁰⁾+O₂d₂, where the (d₁, d₂) is suchthat the (d₁) belongs to a set of integers {0, 1, . . . , min(N₁,L₁)−1},the (d₂) belongs to a set of integers {0, 1, . . . , min(N₂,L₂)−1}, and(d₁,d₂)≠(0, 0).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS 361 stored in the memory 360 in order tocontrol the overall operation of the UE 116. For example, the processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as processes for CSI reportingon an uplink channel. The processor 340 can move data into or out of thememory 360 as required by an executing process. In some embodiments, theprocessor 340 is configured to execute the applications 362 based on theOS 361 or in response to signals received from eNBs or an operator. Theprocessor 340 is also coupled to the I/O interface 345, which providesthe UE 116 with the ability to connect to other devices, such as laptopcomputers and handheld computers. The I/O interface 345 is thecommunication path between these accessories and the processor 340.

In some embodiments, the processor 340 is capable of determining thefirst PMI (i₁) and the second PMI (i₂) indicating an LC pre-coder thatcorresponds to a weighted linear combination of a first beam and asecond beam.

In such embodiments, the first PMI (i₁) includes a first beam indicator(i_(1,1), i_(1,2)) and a second beam indicator (i_(1,3)) that indicatethe first beam and a distance (d₁, d₂) of the second beam in accordancewith the first beam, respectively.

In such embodiments, a (i_(1,1)) and a (i_(1,2)) indicate an index ofthe first beam in a first dimension and a second dimension,respectively.

In such embodiments, a (d₁) and a (d₂) indicate a distance of the secondbeam from the first beam in the first dimension and the seconddimension, respectively.

In such embodiments, the second PMI (i₂) indicates weights assigned tothe first beam and the second beam.

In such embodiments, the first PMI (i₁) includes a relative powerindicator (RPI) (I_(p)) indicating a power of a weight assigned to thesecond beam relative to a power of a weight assigned to the first beam,and wherein the power of the weight assigned to the first beam is set to1 and the power of the weight assigned to the second beam is set to avalue among {0, √{square root over (¼)}, √{square root over (½)}, 1}.

In such embodiments, the first beam and the second beam correspond totwo discrete Fourier transform (DFT) beams selected from an oversampledDFT codebook comprising DFT beams:

${v_{l_{1},l_{2}} = \begin{bmatrix}u_{l_{2}} & {e^{j\frac{2\pi \; l_{1}}{O_{1}N_{1}}}u_{l_{2}}} & \ldots & {e^{j\frac{2\pi \; {l_{1}{({N_{1} - 1})}}}{O_{1}N_{1}}}u_{l_{2}}}\end{bmatrix}^{T}},{{u_{l_{2}} = {{1{\mspace{11mu} \;}{if}\mspace{14mu} N_{2}} = 1}};{u_{l_{2}} = \begin{bmatrix}1 & e^{j\frac{2\pi \; l_{2}}{O_{2}N_{2}}} & \ldots & e^{j\frac{2\pi \; {l_{2}{({N_{2} - 1})}}}{O_{2}N_{2}}}\end{bmatrix}}}$

otherwise, 0≤l₁≤O₁N₁−1, and 0≤l₂≤O₂N₂−1, where N₁ and N₂ indicate afirst and second number of antenna ports in the first and the seconddimensions, respectively, and O₁ and O₂ indicate a first and a secondoversampling factors in the first and second dimensions, respectively.

In such embodiments, the distance (d₁, d₂) of the second beam relativeto a first beam index (k₁ ⁽⁰⁾, k₂ ⁽⁰⁾) indicated by the first beamindicator (i_(1,1), i_(1,2)) is such that the (d₁) belongs to a set ofintegers {0, 1, . . . , L₁−1} and the (d₂) belongs to a set of integers{0, 1, . . . , L₂−1}, respectively.

In such embodiments, a beam group size (L₁, L₂) is determined by:N₁≥N₂>1: L₁=min(N₁,4), L₂=2; N₂>N₁>1: L₂=min(N₂,4), L₁=2; and N₂=1:L_(t)=min(N₁,8), L₂=1.

In such embodiments, a second beam index (k₁ ⁽¹⁾, k₂ ⁽¹⁾) is determinedby: k₁ ⁽¹⁾=k₁ ⁽⁰⁾+O₁d₁, k₂ ⁽¹⁾=k₂ ⁽⁰⁾+O₂d₂, where the (d₁,d₂) is suchthat the (d₁) belongs to a set of integers {0, 1, . . . , min(N₁,L₁)−1},the (d₂) belongs to a set of integers {0, 1, . . . , min(N₂,L₂)−1}, and(d₁,d₂)≠(0,0).

In some embodiments, the processor 340 is capable of mapping between thesecond beam indicator (i_(1,3)) and the distance (d₁, d₂) of the secondbeam based on a table given by:

N₁ ≥ N₂, N₂ > N₁, N₁ ≥ 4, N₁ = 3, N₁ = 2, N₂ ≥ 4, N₂ = 3, N₁ ≥ 8 N₁ = 2,N₁ = 4, Value of N₂ ≠ 1 N₂ = 2 N₂ = 2 N₁ ≠ 1 N₁ = 2 N₂ = 1 N₂ = 1 N₂ = 1i_(1, 3) d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ d₁ d₂ 0 1 0 1 0 1 0 01 0 1 1 0 1 0 1 0 1 2 0 2 0 0 1 0 2 0 2 2 0 2 0 2 3 0 0 1 1 1 0 3 1 0 30 3 0 3 0 1 1 1 1 0 1 1 4 0 4 1 1 2 1 1 1 1 2 5 0 5 2 1 1 2 6 0 6 3 1 13 7 0

In some embodiments, the processor 340 is capable of reporting a singlewideband (WB) bit stream that indicates three components jointly, the(i_(1,1), i_(1,2)) indicating the first beam, the (i_(1,3)) indicatingthe distance (d₁, d₂) of the second beam from the first beam, and the(I_(p)) indicating the power of the weight assigned to the second beam.

In some embodiments, the processor 340 is capable of reporting multipleWB bit streams that indicate three components separately, a first bitstream for the (i_(1,1), i_(1,2)) indicating the first beam, and eithera second bit stream jointly indicating the (i_(1,3)) and the (I_(p)) forthe second beam or a second bit stream and a third bit stream separatelyindicating the (i_(1,3)) and the (I_(p)) for the second beam,respectively.

In some embodiments, the processor 340 is capable of separating thedistance (d₁, d₂) of the second beam in accordance with a PMI(i_(1,1-2), i_(1,2-2)), wherein the (d₁) of the distance (d₁, d₂)corresponds to a (i_(1,1-2)) of the PMI (i_(1,1-2), i_(1,2-2)) and the(d₂) of the distance (d₁, d₂) corresponds to a (i_(1,2-2)) of the PMI(i_(1,1-2), i_(1,2-2)), and wherein if one PMI (i₃) or (i_(1,1-2),i_(1,2-2)) is reported to the BS, a bit width for the PMI is determinedby ┌log₂(L₁L₂)┐ and if two PMIs, (i_(1,1-2)) and (i_(1,2-2)), arereported to the BS, bit widths for the two PMIs are determined by┌log₂(L₁)┐ and ┌log₂(L₂)┘, respectively.

The processor 340 is also coupled to the touchscreen 350 and the display355. The operator of the UE 116 can use the touchscreen 350 to enterdata into the UE 116. The display 355 may be a liquid crystal display,light emitting diode display, or other display capable of rendering textand/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

Although FIG. 3 illustrates one example of UE 116, various changes maybe made to FIG. 3. For example, various components in FIG. 3 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, theprocessor 340 could be divided into multiple processors, such as one ormore central processing units (CPUs) and one or more graphics processingunits (GPUs). Also, while FIG. 3 illustrates the UE 116 configured as amobile telephone or smartphone, UEs could be configured to operate asother types of mobile or stationary devices.

FIG. 4A is a high-level diagram of transmit path circuitry 400. Forexample, the transmit path circuitry 400 may be used for an orthogonalfrequency division multiple access (OFDMA) communication. FIG. 4B is ahigh-level diagram of receive path circuitry 450. For example, thereceive path circuitry 450 may be used for an orthogonal frequencydivision multiple access (OFDMA) communication. In FIGS. 4A and 4B, fordownlink communication, the transmit path circuitry 400 may beimplemented in a base station (eNB) 102 or a relay station, and thereceive path circuitry 450 may be implemented in a user equipment (e.g.user equipment 116 of FIG. 1). In other examples, for uplinkcommunication, the receive path circuitry 450 may be implemented in abase station (e.g. eNB 102 of FIG. 1) or a relay station, and thetransmit path circuitry 400 may be implemented in a user equipment (e.g.user equipment 116 of FIG. 1).

Transmit path circuitry 400 comprises channel coding and modulationblock 405, serial-to-parallel (S-to-P) block 410, Size N Inverse FastFourier Transform (IFFT) block 415, parallel-to-serial (P-to-S) block420, add cyclic prefix block 425, and up-converter (UC) 430. Receivepath circuitry 450 comprises down-converter (DC) 455, remove cyclicprefix block 460, serial-to-parallel (S-to-P) block 465, Size N FastFourier Transform (FFT) block 470, parallel-to-serial (P-to-S) block475, and channel decoding and demodulation block 480.

At least some of the components in FIGS. 4A and 4B may be implemented insoftware, while other components may be implemented by configurablehardware or a mixture of software and configurable hardware. Inparticular, it is noted that the FFT blocks and the IFFT blocksdescribed in this disclosure document may be implemented as configurablesoftware algorithms, where the value of Size N may be modified accordingto the implementation.

Furthermore, although this disclosure is directed to an embodiment thatimplements the Fast Fourier Transform and the Inverse Fast FourierTransform, this is by way of illustration only and should not beconstrued to limit the scope of the disclosure. It may be appreciatedthat in an alternate embodiment of the disclosure, the Fast FourierTransform functions and the Inverse Fast Fourier Transform functions mayeasily be replaced by discrete Fourier transform (DFT) functions andinverse discrete Fourier transform (IDFT) functions, respectively. Itmay be appreciated that for DFT and IDFT functions, the value of the Nvariable may be any integer number (i.e., 1, 4, 3, 4, etc.), while forFFT and IFFT functions, the value of the N variable may be any integernumber that is a power of two (i.e., 1, 2, 4, 8, 16, etc.).

In transmit path circuitry 400, channel coding and modulation block 405receives a set of information bits, applies coding (e.g., LDPC coding)and modulates (e.g., quadrature phase shift keying (QPSK) or quadratureamplitude modulation (QAM)) the input bits to produce a sequence offrequency-domain modulation symbols. Serial-to-parallel block 410converts (i.e., de-multiplexes) the serial modulated symbols to paralleldata to produce N parallel symbol streams where N is the IFFT/FFT sizeused in BS 102 and UE 116. Size N IFFT block 415 then performs an IFFToperation on the N parallel symbol streams to produce time-domain outputsignals. Parallel-to-serial block 420 converts (i.e., multiplexes) theparallel time-domain output symbols from Size N IFFT block 415 toproduce a serial time-domain signal. Add cyclic prefix block 425 theninserts a cyclic prefix to the time-domain signal. Finally, up-converter430 modulates (i.e., up-converts) the output of add cyclic prefix block425 to RF frequency for transmission via a wireless channel. The signalmay also be filtered at baseband before conversion to RF frequency.

The transmitted RF signal arrives at UE 116 after passing through thewireless channel, and reverse operations to those at eNB 102 areperformed. Down-converter 455 down-converts the received signal tobaseband frequency, and remove cyclic prefix block 460 removes thecyclic prefix to produce the serial time-domain baseband signal.Serial-to-parallel block 465 converts the time-domain baseband signal toparallel time-domain signals. Size N FFT block 470 then performs an FFTalgorithm to produce N parallel frequency-domain signals.Parallel-to-serial block 475 converts the parallel frequency-domainsignals to a sequence of modulated data symbols. Channel decoding anddemodulation block 480 demodulates and then decodes the modulatedsymbols to recover the original input data stream.

Each of eNBs 101-103 may implement a transmit path that is analogous totransmitting in the downlink to user equipment 111-116 and may implementa receive path that is analogous to receiving in the uplink from userequipment 111-116. Similarly, each one of user equipment 111-116 mayimplement a transmit path corresponding to the architecture fortransmitting in the uplink to eNBs 101-103 and may implement a receivepath corresponding to the architecture for receiving in the downlinkfrom eNBs 101-103.

Various embodiments of the present disclosure provides for ahigh-performance, scalability with respect to the number and geometry oftransmit antennas, and a flexible CSI feedback (e.g., reporting)framework and structure for LTE enhancements when FD-MIMO with largetwo-dimensional antenna arrays is supported. To achieve highperformance, more accurate CSI in terms MIMO channel is needed at theeNB especially for FDD scenarios. In this case, embodiments of thepresent disclosure recognize that the previous LTE (e.g. Rel. 12)precoding framework (PMI-based feedback) may need to be replaced. Inthis disclosure, properties of FD-MIMO are factored in for the presentdisclosure. For example, the use of closely spaced large 2D antennaarrays that is primarily geared toward high beamforming gain rather thanspatial multiplexing along with relatively small angular spread for eachUE. Therefore, compression or dimensionality reduction of the channelfeedback in accordance with a fixed set of basic functions and vectorsmay be achieved. In another example, updated channel feedback parameters(e.g., the channel angular spreads) may be obtained at low mobilityusing UE-specific higher-layer signaling. In addition, a CSI reporting(feedback) may also be performed cumulatively.

Another embodiment of the present disclosure incorporates a CSIreporting method and procedure with a reduced PMI feedback. This PMIreporting at a lower rate pertains to long-term DL channel statisticsand represents a choice of a group of precoding vectors recommended by aUE to an eNB. The present disclosure also includes a DL transmissionmethod wherein an eNB transmits data to a UE over a plurality ofbeamforming vectors while utilizing an open-loop diversity scheme.Accordingly, the use of long-term precoding ensures that open-looptransmit diversity is applied only across a limited number of ports(rather than all the ports available for FD-MIMO, e.g., 64). This avoidshaving to support excessively high dimension for open-loop transmitdiversity that reduces CSI feedback overhead and improves robustnesswhen CSI measurement quality is questionable.

FIG. 5 illustrates an example structure for a DL subframe 500 accordingto embodiments of the present disclosure. An embodiment of the DLsubframe 500 shown in FIG. 1 is for illustration only. Other embodimentsmay be used without departing from the scope of the present disclosure.The downlink subframe (DL SF) 510 includes two slots 520 and a total ofN_(symb) ^(DL) symbols for transmitting of data information and downlinkcontrol information (DCI). The first M_(symb) ^(DL) SF symbols are usedto transmit PDCCHs and other control channels 530 (not shown in FIG. 5).The remaining Z SF symbols are primarily used to transmit physicaldownlink shared channels (PDSCHs) 540, 542, 544, 546, and 548 orenhanced physical downlink control channels (EPDCCHs) 550, 552, 554, and556. A transmission bandwidth (BW) comprises frequency resource unitsreferred to as resource blocks (RBs). Each RB comprises either N_(sc)^(RB) sub-carriers or resource elements (REs) (such as 12 Res). A unitof one RB over one subframe is referred to as a physical RB (PRB). A UEis allocated to M_(PDSCI) RBs for a total ofZ=O_(F)+└(n_(s0)+y·N_(EPDCCH))/D┘ REs for a PDSCH transmission BW. AnEPDCCH transmission is achieved in either one RB or multiple of RBs.

FIG. 6 illustrates an example transmission structure of a physicaluplink shared channel (PUSCH) subframe or a physical uplink controlchannel (PUCCH) subframe 600. Embodiments of the transmission structurefor the PUSCH or the PUCCH over the UL subframe shown in FIG. 6 is forillustration only. Other embodiments could be used without departingfrom the scope of the present disclosure. A UL subframe 610 includes twoslots. Each slot 620 includes N_(symb) ^(UL) symbols 630 fortransmitting data information, uplink control information (UCI),demodulation reference signals (DMRS), or sounding RSs (SRSs). Afrequency resource unit of an UL system BW is a RB. A UE is allocated toN_(RB) RBs 640 for a total of N_(RB)·N_(sc) ^(RB) resource elements(Res) for a transmission BW. For a PUCCH, N_(RB)=1. A last subframesymbol is used to multiplex SRS transmissions 650 from one or more UEs.A number of subframe symbols that are available for data/UCI/DMRStransmission is N_(symb)=2·(N_(symb) ^(UL)−1)−N_(SRS), where N_(SRS)=1if a last subframe symbol is used to transmit SRS and N_(SRS)=0otherwise.

FIG. 7 illustrates an example transmitter block diagram 700 for aphysical downlink shared channel (PDSCH) subframe according toembodiments of the present disclosure. An embodiment of the PDSCHtransmitter block diagram 700 shown in FIG. 7 is for illustration only.Other embodiments are used without departing from the scope of thepresent disclosure.

Information bits 710 are encoded by an encoder 720 (such as a turboencoder) and modulated by a modulator 730, for example using aquadrature phase shift keying (QPSK) modulation. A Serial to Parallel(S/P) converter 740 generates M modulation symbols that are subsequentlyprovided to a mapper 750 to be mapped to REs selected by a transmissionBW selection unit 755 for an assigned PDSCH transmission BW, unit 760applies an inverse fast Fourier transform (IFFT). An output is thenserialized by a parallel to a serial (P/S) converter 770 to create atime domain signal, filtering is applied by a filter 780, and thensignal is transmitted. Additional functionalities, such as datascrambling, a cyclic prefix insertion, a time windowing, aninterleaving, and others are well known in the art and are not shown forbrevity.

FIG. 8 illustrates an example receiver block diagram 800 for a packetdata shared channel (PDSCH) subframe according to embodiments of thepresent disclosure. An embodiment of the PDSCH receiver block diagram800 shown in FIG. 8 is for illustration only. One or more of thecomponents illustrated in FIG. 8 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments can beused without departing from the scope of the present disclosure.

A received signal 810 is filtered by a filter 820, and then is output toa resource element (RE) demapping block 830. The RE demapping block 830assigns a reception bandwidth (BW) that is selected by a BW selector835. The BW selector 835 is configured to control a transmission BW. Afast Fourier transform (FFT) circuit 840 applies a FFT. The output ofthe FFT circuit 840 is serialized by a parallel-to-serial converter 850.Subsequently, a demodulator 860 coherently demodulates data symbols byapplying a channel estimate obtained from a demodulation referencesignal (DMRS) or a common reference signal (CRS) (not shown), and then adecoder 870 decodes demodulated data to provide an estimate of theinformation data bits 880. The decoder 870 can be configured toimplement any decoding process, such as a turbo decoding process.Additional functionalities such as time-windowing, a cyclic prefixremoval, a de-scrambling, channel estimation, and a de-interleaving arenot shown for brevity.

FIG. 9 illustrates a transmitter block diagram 900 for a physical uplinkshared channel (PUSCH) subframe according to embodiments of the presentdisclosure. One or more of the components illustrated in FIG. 9 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.An embodiment of the PUSCH transmitter block diagram 900 shown in FIG. 9is for illustration only. Other embodiments are used without departingfrom the scope of the present disclosure.

Information data bits 910 are encoded by an encoder 920 and modulated bya modulator 930. Encoder 920 can be configured to implement any encodingprocess, such as a turbo coding process. A discrete Fourier transform(DFT) circuitry 940 applies a DFT on the modulated data bits. REs aremapped by an RE mapping circuit 950. The REs corresponding to anassigned PUSCH transmission BW are selected by a transmission BWselection unit 955. An inverse FFT (IFFT) circuit 960 applies an IFFT tothe output of the RE mapping circuit 950. After a cyclic prefixinsertion (not shown), filter 970 applies a filtering. The filteredsignal then is transmitted.

FIG. 10 illustrates an example receiver block diagram 1000 for a PUSCHsubframe according to embodiments of the present disclosure. Anembodiment of the PUSCH receiver block diagram 1000 shown in FIG. 10 isfor illustration only. One or more of the components illustrated in FIG.10 can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

A received signal 1010 is filtered by a filter 1020. Subsequently, aftera cyclic prefix is removed (not shown), an FFT circuit 1030 applies anFFT. REs are mapped by an RE mapping circuit 1040. REs corresponding toan assigned PUSCH reception BW are selected by a reception BW selector1045. An inverse DFT (IDFT) circuit 1050 applies an IDFT. Demodulator1060 receives an output from IDFT circuit 1050 and coherentlydemodulates data symbols by applying a channel estimate obtained from aDMRS (not shown). A decoder 1070 decodes the demodulated data to providean estimate of the information data bits 1080. The decoder 1070 can beconfigured to implement any decoding process, such as a turbo decodingprocess.

FIG. 11 illustrates an example configuration of a two dimensional (2D)antenna array 1100 which is constructed from 16 dual-polarized antennaelements arranged in a 4×4 rectangular format according to embodimentsof the present disclosure. In this illustration, each labelled antennaelement is logically mapped onto a single antenna port. Two alternativelabelling conventions are depicted for illustrative purposes (such as ahorizontal first in 1110 and a vertical first in 1120). In oneembodiment, one antenna port corresponds to multiple antenna elements(such as physical antennas) combined via a virtualization. This 4×4 dualpolarized array is then viewed as 16×2=32-element array of elements. Thevertical dimension (such as including 4 rows) facilitates an elevationbeamforming in addition to an azimuthal beamforming across a horizontaldimension including 4 columns of dual polarized antennas. A MIMOprecoding in Rel. 12 of the LTE standardization was largely designed tooffer a precoding gain for one-dimensional antenna array. While fixedbeamforming (such as antenna virtualization) is implemented across anelevation dimension, it is unable to reap a potential gain offered by aspatial and frequency selective nature of channels.

In 3GPP LTE specification, MIMO precoding (for beamforming or spatialmultiplexing) can be facilitated via precoding matrix index (PMI)reporting as a component of channel state information (CSI) reporting.The PMI report is derived from one of the following sets of standardizedcodebooks: two antenna ports (single-stage); four antenna ports(single-stage or dual-stage); eight antenna ports (dual-stage);configurable dual-stage eMIMO-Type of “CLASS A” codebook for eight,twelve, or sixteen antenna ports (also known as “nonPrecoded”); andsingle-stage eMIMO-Type of “CLASS B” codebook for two, four, or eightantenna ports (also known as “beamformed”).

If an eNodeB follows a PMI recommendation from a UE, the eNB is expectedto precode the eNB's transmitted signal according to a recommendedprecoding vector or matrix for a given subframe and RB. Regardlesswhether the eNB follows this recommendation, the UE is configured toreport a PMI according to a configured precoding codebook. Here a PMI,which may consist of a single index or a pair of indices, is associatedwith a precoding matrix W in an associated codebook.

When dual-stage class A codebook is configured, a resulting precodingmatrix can be described in equation (1). That is, the first stageprecoder can be described as a Kronecker product of a first and a secondprecoding vector (or matrix), which can be associated with a first and asecond dimension, respectively. This type is termed partial KroneckerProduct (partial KP) codebook. The subscripts m and n inW_(m,n)(i_(m,n)) denote precoding stage (first or second stage) anddimension (first or second dimension), respectively. Each of theprecoding matrices W_(m,n) can be described as a function of an indexwhich serves as a PMI component. As a result, the precoding matrix W canbe described as a function of 3 PMI components. The first stage pertainsto a long-term component. Therefore it is associated with long-termchannel statistics such as the aforementioned AoD profile and AoDspread. On the other hand, the second stage pertains to a short-termcomponent which performs selection, co-phasing, or any linear operationto the first component precoder W_(1,1)(i_(1,1))⊗W_(1,2)(i_(1,2)). Theprecoder W₂(i₂), therefore, performs a linear transformation of thelong-term component such as a linear combination of a set of basicfunctions or vectors associated with the column vectors ofW_(1,1)(i_(1,1))⊗W_(1,2)(i_(1,2))).

$\begin{matrix}{{W\left( {i_{1,1},i_{1,2},i_{2}} \right)} = {\underset{\underset{W_{1}{({i_{1,1},i_{1,2}})}}{}}{\left( {{W_{1,1}\left( i_{1,1} \right)} \otimes {W_{1,2}\left( i_{1,2} \right)}} \right)}{W_{2}\left( i_{2} \right)}}} & {{Equation}\mspace{14mu} (1)}\end{matrix}$

The above discussion assumes that the serving eNB transmits and a servedUE measures non-precoded CSI-RS (NP CSI-RS). That is, a cell-specificone-to-one mapping between CSI-RS port and TXRU is utilized. Here,different CSI-RS ports have the same wide beam width and direction andhence generally cell wide coverage. This use case can be realized whenthe eNB configures the UE with “CLASS A” eMIMO-Type which corresponds toNP CSI-RS. Other than CQI and RI, CSI reports associated with “CLASS A”or “nonPrecoded” eMIMO-Type include a three-component PMI {i_(1,1),i_(1,2), i₂}.

Another type of CSI-RS applicable to FD-MIMO is beamformed CSI-RS (BFCSI-RS). In this case, beamforming operation, either cell-specific (withK>1 CSI-RS resources) or UE-specific (with K=1 CSI-RS resource), isapplied on a non-zero-power (NZP) CSI-RS resource (consisting ofmultiple ports). Here, (at least at a given time/frequency) CSI-RS portshave narrow beam widths and hence not cell wide coverage, and (at leastfrom the eNB perspective) at least some CSI-RS port-resourcecombinations have different beam directions. This beamforming operationis intended to increase CSI-RS coverage.

In addition, when UE-specific beamforming is applied to CSI-RS resource(termed the UE-specific or UE-specifically beamformed CSI-RS), CSI-RSoverhead reduction is possible. UE complexity reduction is also evidentsince the configured number of ports tends to be much smaller than NPCSI-RS counterpart of the UE. When a UE is configured to receive BFCSI-RS from a serving eNB, the UE can be configured to report PMIparameter(s) associated with a second-stage precoder without theassociated first-stage precoder or, in general, associated with asingle-stage precoder/codebook. This use case can be realized when theeNB configures the UE with “CLASS B” eMIMO-Type which corresponds to BFCSI-RS. Other than CQI and RI, CSI reports associated with “CLASS B” or“beamformed” eMIMO-Type (with one CSI-RS resource and alternativecodebook) include a one-component PMI n. Although a single PMI definedwith respect to a distinct codebook, this PMI can be associated with thesecond-stage PMI component of “CLASS A”/“nonPrecoded” codebooks i₂.

Therefore, given a precoding codebook (a set of precoding matrices), aUE measures a CSI-RS in a subframe designated to carry CSI-RS,calculates/determines a CSI (including PMI, RI, and CQI where each ofthese three CSI parameters can consist of multiple components) based onthe measurement, and reports the calculated CSI to a serving eNB. Inparticular, this PMI is an index of a recommended precoding matrix inthe precoding codebook. Similar to that for the first type, differentprecoding codebooks can be used for different values of RI. The measuredCSI-RS can be one of the two types: non-precoded (NP) CSI-RS andbeamformed (BF) CSI-RS. As mentioned, in Rel. 13, the support of thesetwo types of CSI-RS is given in terms of two eMIMO-Types: “CLASS A”(with one CSI-RS resource) and “CLASS B” (with one or a plurality ofCSI-RS resources), respectively.

In scenarios where DL long-term channel statistics can be measuredthrough UL signals at a serving eNB, UE-specific BF CSI-RS can bereadily used. This is typically feasible when UL-DL duplex distance issufficiently small. When this condition does not hold, however, some UEfeedback is necessary for the eNB to obtain an estimate of DL long-termchannel statistics (or any of representation thereof). To facilitatesuch a procedure, a first BF CSI-RS transmitted with periodicity T1 (ms)and a second NP CSI-RS transmitted with periodicity T2 (ms), whereT1≤T2. This approach is termed hybrid CSI-RS. The implementation ofhybrid CSI-RS is largely dependent on the definition of CSI process andNZP CSI-RS resource.

In LTE specification, the aforementioned precoding codebooks areutilized for CSI reporting. Two schemes of CSI reporting modes aresupported (e.g., PUSCH-based aperiodic CSI (A-CSI) and PUCCH-basedperiodic CSI (P-CSI)). In each scheme, different modes are defined basedon frequency selectivity of CQI and/or PMI, that is, whether wideband orsubband reporting is performed. The supported CSI reporting modes aregiven in Table 1.

TABLE 1 CQI and PMI Feedback Types for PUSCH CSI reporting Modes PMIFeedback Type No Single Multiple PMI PMI PMI PUSCH CQI Wideband Mode 1-2Feedback Type (wideband CQI) UE Selected Mode 2-0 Mode 2-2 (subband CQI)Higher Layer- Mode 3-0 Mode 3-1 Mode 3-2 configured (subband CQI)

TABLE 2 CQI and PMI Feedback Types for PUCCH CSI reporting Modes PMIFeedback Type No Single PMI PMI PUCCH CQI Wideband Mode 1-0 Mode 1-1Feedback Type (wideband CQI) UE Selected Mode 2-0 Mode 2-1 (subband CQI)

According to the WI, the hybrid CSI reporting based on non-precoded andbeamformed CSI-RS associated with two eMIMO-Types may be supported inLTE specification.

In the present disclosure, for brevity, FDD is considered as the duplexmethod for both DL and UL signaling but the embodiments of the presentdisclosure are also directly applicable to TDD.

Throughout the present disclosure, 2D dual-polarized array is usedsolely for illustrative purposes, unless stated otherwise. Extensions to2D single-polarized array are straightforward for those skilled in theart.

Terms such as “non-precoded” (or “NP”) CSI-RS and “beamformed” (or “BF”)CSI-RS are used throughout this present disclosure. The essence of thispresent disclosure does not change when different terms or names areused to refer to these two CSI-RS types. The same holds for CSI-RSresource. CSI-RS resources associated with these two types of CSI-RS canbe referred to as “a first CSI-RS resource” and “a second CSI-RSresource,” or “CSI-RS-A resource” and “CSI-RS-B resource.” Subsequently,the labels “NP” and “BF” (or “np” and “bf”) are exemplary and can besubstituted with other labels such as “1” and “2.” “A” or “B.”Alternatively, instead of using categories such as CSI-RS type or CSI-RSresource type, a category of CSI reporting class can also be used. Forinstance, NP CSI-RS is associated with eMIMO-Type of “CLASS A” whileUE-specific BF CSI-RS is associated with eMIMO-Type of “CLASS B” withone CSI-RS resource.

FIG. 12 illustrates an example dual-polarized antenna port layouts for{2, 4, 8, 12, 16} ports 1200 according to embodiments of the presentdisclosure. An embodiment of the dual-polarized antenna port layouts for{2, 4, 8, 12, 16} ports 1200 shown in FIG. 12 is for illustration only.One or more of the components illustrated in FIG. 12 can be implementedin specialized circuitry configured to perform the noted functions orone or more of the components can be implemented by one or moreprocessors executing instructions to perform the noted functions. Otherembodiments are used without departing from the scope of the presentdisclosure.

As shown in FIG. 12, 2D antenna arrays are constructed from N₁×N₂dual-polarized antenna elements arranged in a (N₁, N₂) rectangularformat for 2, 4, 8, 12, 16 antenna ports. In FIG. 12, each antennaelement is logically mapped onto a single antenna port. In general, oneantenna port may correspond to multiple antenna elements (physicalantennas) combined via a virtualization. This N₁×N₂ dual polarized arraycan then be viewed as 2N₁N₂-element array of elements.

The first dimension consists of N₁ columns and facilitates azimuthbeamforming. The second dimension similarly consists of N₂ rows andallows elevation beamforming. MIMO precoding in LTE specification waslargely designed to offer precoding (beamforming) gain forone-dimensional (1D) antenna array using 2, 4, 8 antenna ports, whichcorrespond to (N₁, N₂) belonging to {(1, 1), (2, 1), (4, 1)}. Whilefixed beamforming (i.e. antenna virtualization) can be implementedacross the elevation dimension, it is unable to reap the potential gainoffered by the spatial and frequency selective nature of the channel.Therefore, MIMO precoding in LTE specification is designed to offerprecoding gain for two-dimensional (2D) antenna array using 8, 12, 16antenna ports, which correspond to (N₁, N₂) belonging to {(2, 2), (2,3), (3, 2), (8, 1), (4, 2), (2, 4)}.

Although (N₁, N₂)=(6, 1) case has not been supported in LTEspecification, it may be supported in future releases. The embodimentsof the present disclosure are general and are applicable to any (N₁, N₂)values including (N₁, N₂)=(6, 1). The first and second dimensions asshown in FIG. 12 are for illustration only. The present disclosure isapplicable to the case, in which the first and second dimensions areswapped, i.e., first and second dimensions respectively correspond toelevation and azimuth or any other pair of directions.

For 8 antenna ports {15,16,17,18,19,20,21,22}, 12 antenna ports{15,16,17,18,19,20,21,22,23,24,25,26}, 16 antenna ports{15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30}, and UE configuredwith higher layer parameter eMIMO-Type, and eMIMO-Type is set to “CLASSA,” each PMI value corresponds to three codebook indices given in Table4, where the quantities φ_(n), u_(m) and v_(l,m) are given by equation(2):

$\begin{matrix}{{\phi_{n} = e^{j\; \pi \; {n/2}}}{u_{m} = \begin{bmatrix}1 & e^{j\frac{{2\pi \; m}\;}{O_{2}N_{2}}} & \ldots & e^{j\frac{2\pi \; {m{({N_{2} - 1})}}}{O_{2}N_{2}}}\end{bmatrix}}{v_{l,m} = \begin{bmatrix}u_{m} & {e^{j\frac{2\pi \; l}{O_{1}N_{1}}}u_{m}} & \ldots & {e^{j\frac{2\pi \; {l{({N_{1} - 1})}}}{O_{1}N_{1}}}u_{m}}\end{bmatrix}^{T}}} & (2)\end{matrix}$

The values of N₁, N₂, O₁, and O₂ are configured with the higher-layerparameters codebook-Config-N1, codebook-Config-N2,codebook-Over-Sampling-RateConfig-O1, andcodebook-Over-Sampling-RateConfig-O2, respectively. The supportedconfigurations of (O₁,O₂) and (N₁,N₂) for a given number of CSI-RS portsare given in Table 3. The number of CSI-RS ports, P, is 2N₁N₂.

A UE is not expected to be configured with value of Codebook-Config setto 2 or 3, if the value of codebook-Config-N2 is set to 1. A UE may usei_(1,2)=0 and shall not report i_(1,2) if the value ofcodebook-Config-N2 is set to 1. A first PMI value i₁ corresponds to thecodebook indices pair {i_(1,1),i_(1,2)}, and a second PMI value i₂corresponds to the codebook index i₂ given in Table 4. In some casescodebook subsampling is supported. The sub-sampled codebook for PUCCHmode 2-1 for value of parameter Codebook-Config set to 2, 3, or 4 isdefined in LTE specification for PUCCH Reporting Type 1a.

TABLE 3 Supported configurations of (O₁, O₂) and (N₁, N₂) Number ofCSI-RS antenna ports, P (N₁, N₂) (O₁, O₂) 8 (2, 2) (4, 4), (8, 8) 12 (2,3) (8, 4), (8, 8) (3, 2) (8, 4), (4, 4) 16 (2, 4) (8, 4), (8, 8) (4, 2)(8, 4), (4, 4) (8, 1) (4, —), (8, —)

TABLE 4 Codebook for 1-layer CSI reporting using antenna ports 15 to14 + P Value of i₂ Codebook- i_(1,1) i_(1,2) 0 1 Config. 0,1, . . . ,O₁N₁ − 1 0,1, . . . , O₂N₂ − 1 W_(i) _(1,1) _(,i) _(1,2) _(,0) ⁽¹⁾ W_(i)_(1,1) _(,i) _(1,2) _(,1) ⁽¹⁾ 1 i_(1,1) i_(1,2) 2 3 0,1, . . . , O₁N₁ −1 0,1, . . . , O₂N₂ − 1 W_(i) _(1,1) _(,i) _(1,2) _(,2) ⁽¹⁾ W_(i) _(1,1)_(,i) _(1,2) _(,3) ⁽¹⁾${{where}\mspace{14mu} W_{l,m,n}^{(1)}} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{l,m} \\{\; {\phi_{n}v_{l,m}}}\end{bmatrix}}$ Value of i₂ Codebook- i_(1,1) i_(1,2) 0 1 Config. 2$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(,0) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,1) ⁽¹⁾ i_(1,1) i_(1,2) 2 3$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(,2) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,3) ⁽¹⁾ Value of i₂ Codebook-i_(1,1) i_(1,2) 4 5 Config. 2$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(+1,2i)_(1,2) _(,0) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i) _(1,2) _(,1) ⁽¹⁾ i_(1,1) i_(1,2)6 7 $0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(+1,2i)_(1,2) _(,2) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i) _(1,2) _(,3) ⁽¹⁾ Value of i₂Codebook- i_(1,1) i_(1,2) 8 9 Config. 2$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(+1,0) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(+1,1) ⁽¹⁾ i_(1,1) i_(1,2) 1011 $0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(+1,2) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(+1,3) ⁽¹⁾ Value of i₂Codebook- i_(1,1) i_(1,2) 12 13 Config 2$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(+1,2i)_(1,2) _(+1,0) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i) _(1,2) _(+1,1) ⁽¹⁾ i_(1,1)i_(1,2) 14 15 $0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(+1,2i)_(1,2) _(+1,2) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i) _(1,2) _(+1,3) ⁽¹⁾${{where}\mspace{14mu} W_{l,m,n}^{(1)}} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{l,m} \\{\phi_{n}v_{l,m}}\end{bmatrix}}$ Value of i₂ Codebook- i_(1,1) i_(1,2) 0 1 Config 3$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x,2y,0) ⁽¹⁾ W_(2x,2y,1)⁽¹⁾ i_(1,1) i_(1,2) 2 3 $0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x,2y,2) ⁽¹⁾ W_(2x,2y,3)⁽¹⁾ Value of i₂ Codebook- i_(1,1) i_(1,2) 4 5 Config 3$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+2,2y,0) ⁽¹⁾W_(2x+2,2y,1) ⁽¹⁾ i_(1,1) i_(1,2) 6 7$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+2,2y,2) ⁽¹⁾W_(2x+2,2y,3) ⁽¹⁾ Value of i₂ Codebook- i_(1,1) i_(1,2) 8 9 Config 3$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+1,2y+1,0) ⁽¹⁾W_(2x+1,2y+1,1) ⁽¹⁾ i_(1,1) i_(1,2) 10 11$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+1,2y+1,2) ⁽¹⁾W_(2x+1,2y+1,3) ⁽¹⁾ Value of i₂ Codebook- i_(1,1) i_(1,2) 12 13 Config 3$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+3,2y+1,0) ⁽¹⁾W_(2x+3,2y+1,1) ⁽¹⁾ i_(1,1) i_(1,2) 14 15$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+3,2y+1,2) ⁽¹⁾W_(2x+3,2y+1,3) ⁽¹⁾$\quad{{{{where}\mspace{14mu} x} = i_{1,1}},{y = i_{1,2}},{W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{l,m} \\{\phi_{n}v_{l,m}}\end{bmatrix}}},{{{if}\mspace{14mu} N_{1}} \geq N_{2}}}$${x = i_{1,2}},{y = i_{1,1}},{W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{m,l} \\{\phi_{n}v_{m,l}}\end{bmatrix}}},{{{if}\mspace{14mu} N_{1}} < N_{2}}$ Value of i₂Codebook- i_(1,1) i_(1,2) 0 1 Config 4$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x,2y,0) ⁽¹⁾ W_(2x,2y,1)⁽¹⁾ i_(1,1) i_(1,2) 2 3 $0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x,2y,2) ⁽¹⁾ W_(2x,2y,3)⁽¹⁾ Value of i₂ Codebook- i_(1,1) i_(1,2) 4 5 Config 4$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+1,2y,0) ⁽¹⁾W_(2x+1,2y,1) ⁽¹⁾ i_(1,1) i_(1,2) 6 7$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+1,2y,2) ⁽¹⁾W_(2x+1,2y,3) ⁽¹⁾ Value of i₂ Codebook- i_(1,1) i_(1,2) 8 9 Config 4$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+2,2y,0) ⁽¹⁾W_(2x+2,2y,1) ⁽¹⁾ i_(1,1) i_(1,2) 10 11$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+2,2y,2) ⁽¹⁾W_(2x+2,2y,3) ⁽¹⁾ Value of i₂ Codebook- i_(1,1) i_(1,2) 12 13 Config 4$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+3,2y,0) ⁽¹⁾W_(2x+3,2y,1) ⁽¹⁾ i_(1,1) i_(1,2) 14 15$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2x+3,2y,2) ⁽¹⁾W_(2x+3,2y,3) ⁽¹⁾$\quad{{{{where}\mspace{14mu} x} = i_{1,1}},{y = i_{1,2}},{W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{l,m} \\{\phi_{n}v_{l,m}}\end{bmatrix}}},{{{if}\mspace{14mu} N_{1}} \geq N_{2}}}$${x = i_{1,2}},{y = i_{1,1}},{W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{m,l} \\{\phi_{n}v_{m,l}}\end{bmatrix}}},{{{if}\mspace{14mu} N_{1}} < N_{2}}$

The mapping between Codebook-Config parameter to rank 1 beam groupingindicated by (i_(1,1), i_(1,2)) is illustrated in FIG. 29. As shown,Codebook-Config=1 corresponds to one beam (black square located at (0,0)), and Codebook-Config=2, 3, 4 correspond to 4 beams (shown as blacksquares) which are located inside the (4, 2) beam grid depending on theCodebook-Config value.

FIG. 13 illustrates an example dual-polarized antenna port layouts for{20, 24, 28, 32} ports 1300 according to embodiments of the presentdisclosure. An embodiment of the dual-polarized antenna port layouts for{20, 24, 28, 32} ports 1300 shown in FIG. 13 is for illustration only.One or more of the components illustrated in FIG. 13 can be implementedin specialized circuitry configured to perform the noted functions orone or more of the components can be implemented by one or moreprocessors executing instructions to perform the noted functions. Otherembodiments are used without departing from the scope of the presentdisclosure.

Note that Rel. 10 8-Tx and Rel. 12 4-Tx codebooks in LTE specificationcan be mapped to Codebook-Config=4 because Rel. 10 8-Tx and Rel. 12 4-Txcodebooks correspond to 1D antenna port layouts. An eFD-MIMO may support{20, 24, 28, 32} antenna ports in LTE Rel. 14 of LTE specification.Assuming rectangular (ID or 2D) port layouts, there are several possible(N₁, N₂) values for {20, 24, 28, 32} ports (as shown in Table 6). Anillustration of 1D and 2D antenna port layouts for these (N₁,N₂) valuesare shown in FIG. 13.

TABLE 6 Supported configurations of (O₁, O₂) and (N₁, N₂) Number ofCSI-RS antenna ports, P (N₁, N₂) (O₁, O₂) 20  (1, 10) (—, 4), (—, 8) (2,5) (8, 4), (8, 8) (5, 2) (8, 4), (4, 4) (10, 1)  (4, —), (8, —) 24  (1,12) (—, 4), (—, 8) (2, 6) (8, 4), (8, 8) (3, 4) (8, 4), (8, 8) (4, 3)(8, 4), (4, 4) (6, 2) (8, 4), (4, 4) (12, 1)  (4, —), (8, —) 28  (1, 14)(—, 4), (—, 8) (2, 7) (8, 4), (8, 8) (7, 2) (8, 4), (4, 4) (14, 1)  (4,—), (8, —) 32  (1, 16) (—, 4), (—, 8) (2, 8) (8, 4), (8, 8) (4, 4) (4,4), (8, 8) (8, 2) (8, 4), (4, 4) (16, 1)  (4, —), (8, —)

FIG. 14 illustrates an example linear combination pre-coding matrixindicator (PMI) 1400 pre-coder (L=4) according to embodiments of thepresent disclosure. An embodiment of the linear combination pre-codingmatrix indicator (PMI) 1400 pre-coder (L=4) shown in FIG. 14 is forillustration only. One or more of the components illustrated in FIG. 14can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

In some embodiments, a UE is configured with a LC codebook: W=W₁W₂,where W₁ is for WB and long-term first PMI i₁ or PMI pair(i_(1,1),i_(1,2)) feedback, which indicates a 2N₁N₂×2L basis matrix Bwhose columns correspond to 2L beams from a master basis set, and W₂ isfor SB and short-term second PMI i₂ feedback, which indicates acoefficient vector for linear combination.

An illustration of the proposed LC codebook for L=4 is shown in FIG. 14.There are two alternatives for LC codebook depending on whether co-phasefor the two polarizations is reported separately or jointly with thecoefficients. In one example without co-phase, the co-phase for the twopolarizations is not reported separately and is merged with coefficientreporting. In this alternative, the number of beams for linearcombination is 2L (where 2 is for the two polarizations, for example,+45 and −45), and hence a coefficient vector c of length 2L is reported.The rank-1 LC pre-coder in this case is given by W⁽¹⁾=Bc. In anotherexample with co-phase, the co-phase for the two polarizations isreported separately. In this alternative, a coefficient vector c oflength L and a co-phase matrix ϕ for the two polarizations of dimension2L×L are reported. So, the rank-1 LC pre-coder is given by W⁽¹⁾=Bϕc.

In some embodiments, the master basis set is an oversampled DFT codebook(1D or 2D depending on the antenna port layouts), and the basis matrix Bis one of the following types. In one example of Basis 0, the basiscorresponds to L beams for each of the two polarizations, b₀, b₁, . . .b_(L−1) and b₀′, b₁′, . . . b_(L−1)′, i.e. the basis matrix is given by

$B = {\begin{bmatrix}{b_{0},b_{1},{\ldots \mspace{14mu} b_{L - 1}}} & {0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} \\{0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} & {b_{0}^{\prime},b_{1}^{\prime},{\ldots \mspace{14mu} b_{L - 1}^{\prime}}}\end{bmatrix}.}$

In the rest of the present disclosure, it is assumed that the bases forthe two polarizations are the same, i.e., b₀, b₁, . . . b_(L−1)=b₀′,b₁′, . . . b_(L−1)′. The embodiments of the present disclosure, however,are applicable to the case in which the bases for the two polarizationsare different, i.e., b₀, b₁, . . . b_(L−1)≠b₀′, b₁′, . . . b_(L−1)′.

In another example of basis 1, the basis corresponds to L beams b₀, b₁,. . . b_(L−1) for each of the two polarizations and (WB component of)magnitude or power levels m₀ ⁽¹⁾, m₁ ⁽¹⁾, . . . m_(L−1) ⁽¹⁾ for L beams,i.e., the basis matrix is given by

$B = {{\begin{bmatrix}{b_{0},b_{1},\mspace{14mu} {\ldots \mspace{14mu} b_{L - 1}}} & {0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} \\{0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} & {b_{0},b_{1},{\ldots \mspace{14mu} b_{L - 1}}}\end{bmatrix}{{diag}\left( {m_{0}^{(1)},m_{1}^{(1)},{\ldots \mspace{14mu} m_{L - 1}^{(1)}},m_{0}^{(1)},m_{1}^{(1)},{\ldots \mspace{14mu} m_{L - 1}^{(1)}}} \right)}} = {\quad\begin{bmatrix}{{m_{0}^{(1)}b_{0}},{m_{1}^{(1)}b_{1}},{\ldots \mspace{14mu} m_{L - 1}^{(1)}b_{L - 1}}} & {0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} \\{0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} & {{m_{0}^{(1)}b_{0}},{m_{1}^{(1)}b_{1}},{\ldots \mspace{14mu} m_{L - 1}^{(1)}b_{L - 1}}}\end{bmatrix}}}$

where diag(., ., . . . , .) is a diagonal matrix.

In yet another example of basis 2, the basis corresponds to L beams b₀,b₁, . . . b_(L−1) for each of the two polarizations and_(WB componentof) co-phase values ϕ₀ ⁽¹⁾, ϕ₁ ⁽¹⁾, . . . ϕ_(L−1) ⁽¹⁾ for the twopolarizations and L beams, i.e., the basis matrix is given by

$B = {\begin{bmatrix}{b_{0}b_{1}\mspace{14mu} \ldots \mspace{14mu} b_{L - 1}} & {0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} \\{0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} & {b_{0}b_{1}\mspace{14mu} \ldots \mspace{14mu} b_{L - 1}}\end{bmatrix}{\quad{{\begin{bmatrix}e_{0} & e_{1} & \ldots & e_{L - 1} \\{\varphi_{0}^{(1)}e_{0}} & {\varphi_{1}^{(1)}e_{1}} & \ldots & {\varphi_{L - 1}^{(1)}e_{L - 1}}\end{bmatrix} = \begin{bmatrix}b_{0} & b_{1} & \ldots & b_{L - 1} \\{\varphi_{0}^{(1)}b_{0}} & {\varphi_{1}^{(1)}b_{1}} & \ldots & {\varphi_{L - 1}^{(1)}b_{L - 1}}\end{bmatrix}},}}}$

where e_(l) is a length L beam selection vector whose (l+1)-th entry is1 (to select the l-th beam) and the rest of the entries are all zero.

In yet another example of basis 3, the basis corresponds to L beams b₀b₁. . . b_(L−1) for each of the two polarizations (WB component of)co-phase values ϕ₀ ⁽¹⁾, ϕ₁ ⁽¹⁾, . . . ϕ_(L−1) ⁽¹⁾ for the twopolarizations and L beams, and (WB component of) magnitude or powerlevels m₀ ⁽¹⁾, m₁ ⁽¹⁾, . . . m_(L−1) ⁽¹⁾ for L beams, i.e., the basismatrix is given by

$B = {\begin{bmatrix}{b_{0}b_{1}\mspace{14mu} \ldots \mspace{14mu} b_{L - 1}} & {0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} \\{0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} & {b_{0}b_{1}\mspace{14mu} \ldots \mspace{14mu} b_{L - 1}}\end{bmatrix}{\quad{{\begin{bmatrix}e_{0} & e_{1} & \ldots & e_{L - 1} \\{\varphi_{0}^{(1)}e_{0}} & {\varphi_{1}^{(1)}e_{1}} & \ldots & {\varphi_{L - 1}^{(1)}e_{L - 1}}\end{bmatrix}{{diag}\left( {m_{0}^{(1)},m_{1}^{(1)},{\ldots \mspace{14mu} m_{L - 1}^{(1)}}} \right)}} = {\quad{\begin{bmatrix}{m_{0}^{(1)}b_{0}} & {{m_{1}^{(1)}b_{1}}\mspace{11mu}} & \ldots & {m_{L - 1}^{(1)}b_{L - 1}} \\{m_{0}^{(1)}\varphi_{0}^{(1)}b_{0}} & {{m_{1}^{(1)}\varphi_{1}^{(1)}b_{1}}\mspace{11mu}} & \ldots & {m_{L - 1}^{(1)}\varphi_{L - 1}^{(1)}b_{L - 1}}\end{bmatrix}.}}}}}$

In some embodiments, the master basis set is an oversampled DFT codebook(1D or 2D depending on the antenna port layouts), and the basis matrix Bcomprises of one of Basis 0-3 as mentioned above; and a WB B value,where 1≤B≤L for SB selection of B out of L beams.

In the rest of the present disclosure, the notation ϕ_(l) ⁽¹⁾ and ϕ_(l)⁽²⁾, respectively, for WB and SB components of the co-phase ϕ_(l) willbe used. In some embodiments, the co-phase matrix

$\varphi = \begin{bmatrix}e_{0} & e_{1} & \ldots & e_{L - 1} \\{\varphi_{0}e_{0}} & {\varphi_{1}e_{1}} & \ldots & {\varphi_{L - 1}e_{L - 1}}\end{bmatrix}$

comprising of co-phase values ϕ₀, ϕ₁, . . . ϕ_(L−1) for the twopolarizations is according to one of the following types. In one exampleof Single, each co-phase value ϕ_(l) is selected from a single codebook.An example of the codebook is K-PSK codebook, where a few example valuesof K is 2 (BPSK), 4 (QPSK), and 8 (8-PSK). The reported co-phase valuecan either be WB, i.e., ϕ_(l)=ϕ_(l) ⁽¹⁾, or SB, i.e., ϕ_(l)=ϕ_(l) ⁽²⁾.In another example of double, each co-phase value is decomposed asϕ_(l)=ϕ_(l) ⁽¹⁾ϕ_(l) ⁽²⁾ and is selected from a double codebookC_(coph)=C_(coph) ⁽¹⁾C_(coph) ⁽²⁾, where C_(coph) ⁽¹⁾ and C_(coph) ⁽²⁾respectively are codebooks for WB and SB components of the co-phaseϕ_(l) ⁽¹⁾ and ϕ_(l) ⁽²⁾, respectively. An example of the double codebookis

$C_{coph}^{(1)} = {{\left\{ {e^{j\frac{\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{7\pi}{4}}} \right\} \mspace{14mu} {and}\mspace{14mu} C_{coph}^{(2)}} = {\left\{ {e^{j\frac{\pi}{4}},e^{{- j}\frac{\pi}{4}}} \right\}.}}$

In one embodiment, the co-phase for L beams are the same, i.e.,ϕ_(l)=ϕ_(k) for all l, k in {0, 1, . . . , L−1}. In another embodiment,the co-phase for L beams are different, i.e., ϕ_(l)≠ϕ_(k) for all l, kin {0, 1, . . . , L−1}. In this later method, when the co-phase codebookis a double codebook, then at least one of WB and SB co-phase codebook,C_(coph) ⁽¹⁾ and C_(coph) ⁽²⁾, are such that at least ϕ_(l) ⁽¹⁾≠ϕ_(k)⁽¹⁾ or ϕ_(l) ⁽²⁾≠ϕ_(k) ⁽²⁾ for all l, k in {0, 1, . . . , L−1}. Forinstance, ϕ_(l) ⁽¹⁾=ϕ_(k) ⁽¹⁾ and ϕ_(l) ⁽²⁾≠ϕ_(k) ⁽²⁾ (i.e. same WB anddifferent SB co-phase components for all beams) for all l, k in {0, 1, .. . , L−1}.

In the rest of the present disclosure, the coefficient c_(l) isrepresented as m_(l)α_(l), where m_(l) and α_(l) respectively aremagnitude and phase of coefficient c_(l). Similar to the notation usedearlier in the present disclosure, m_(l) ⁽¹⁾ and m_(l) ⁽²⁾ are used forWB and SB components of the magnitude m_(l) (double magnitude codebook)and α_(l) ⁽¹⁾ and α_(l) ⁽²⁾ are used for WB and SB components of thephase α_(l)(double phase codebook).

In some embodiments, the coefficient vector c=[c₀ c₁ . . . c_(2L−1)](Alt 0) or [c₀ c₁ . . . c_(L−1)] (Alt 1) comprises of at least one ofthe following components. In one embodiment, the coefficient vectorcomprises Magnitude {m_(l): l=0, 1, . . . , L−1 or 2L−1}. In suchembodiment, there are two alternatives for coefficient magnitudes:constant-modulus (CM): The magnitudes of all coefficients are the same,i.e., m_(l)=m_(k) for all l, k, and hence not reported; and non-CM: Themagnitudes of coefficients can be different, and the magnitude codebookcan be a combination of the following. In one example of scalar orvector, the coefficient magnitudes are quantized jointly using a vectorcodebook. An example of the vector magnitude codebook is aunit-magnitude vector codebook in which codewords are such that thecodewords are non-negative and their norm is one. Alternatively,coefficient magnitudes are quantized separately using a scalar codebook.An example of the scalar magnitude codebook is a uniform codebook in [0,U], for example U=1. In another example of single or double, thecoefficient magnitude codebook is either a single codebook or a doublecodebook. In case of a single magnitude codebook, magnitude reportingcan either be WB (i.e. m_(l)=m_(l) ⁽¹⁾) or SB (i.e. m_(l)=m_(l) ⁽²⁾).So, non-CM coefficient reporting is either WB or SB. In case of a doublemagnitude codebook, m_(l)=m_(l) ⁽¹⁾m_(l) ⁽²⁾ where at least one of m_(l)⁽¹⁾ and m_(l) ⁽²⁾ reporting is non-CM.

In one embodiment, the coefficient vector comprises phase {α₀: l=0, 1, .. . L−1 or 2L−1}. In such embodiment, there are two alternatives forcoefficient phases. In one example of Vector phase codebook, the phasesof coefficients are quantized jointly using a vector codebook. Anexample of the vector phase codebook is an oversampled DFT codebook. Twoalternatives in this case are as follows. In one example of single, thecoefficient phase vector a=[α₀ α₁ . . . α_(2L−1)] (Alt 0) or [α₀ α₁ . .. α_(L−1)] (Alt 1) is selected from a single vector phase codebook, anexample of which is a DFT codebook with appropriate oversampling factorO, in which a belongs to:

$\begin{matrix}{{{C_{{Coef},0} = \left\{ {{{\begin{bmatrix}1 & e^{j\frac{2\pi \; k}{2{OL}}} & \ldots & e^{j\frac{2\pi \; {k{({{2L} - 1})}}}{2{OL}}}\end{bmatrix}^{T}:k} = 0},1,\ldots \mspace{14mu},{{2{OL}} - 1}} \right\}};}{or}} & \left( {{Alt}\mspace{14mu} 0} \right) \\{C_{{Coef},1} = {\left\{ {{{\begin{bmatrix}1 & e^{j\frac{2\pi \; k}{OL}} & \ldots & e^{j\frac{2\pi \; {k{({L - 1})}}}{OL}}\end{bmatrix}^{T}:k} = 0},1,\ldots \mspace{14mu},{{OL} - 1}} \right\}.}} & \left( {{Alt}\mspace{14mu} 1} \right)\end{matrix}$

In another example of double, the coefficient phase vector is decomposedas a=a⁽¹⁾a⁽²⁾ and is selected from a double vector phase codebook, anexample of which is double DFT codebook in which a⁽¹⁾ and a⁽²⁾ areselected from a DFT codebook with appropriate oversampling factor O suchthat a⁽¹⁾ represents a group of K DFT vectors, and a⁽²⁾ selects one DFTvector from the group. A few examples of K value are 4, 8, and 16. Thisis similar to the Rel. 10 8-Tx dual-stage codebook.

In another example of scalar phase codebook, the phases of coefficientsare quantized separately using a scalar codebook. An example of thescalar phase codebook is K-PSK codebook, where a few example values of Kis 2 (BPSK), 4 (QPSK), and 8 (8-PSK). Two alternatives in this case areas follows. In one alternative of single, each coefficient phase α_(l)is selected from a single codebook, e.g. C_(coef)={1,−1,j,−j}. Inanother alternative of double, each coefficient phase is decomposedα_(l)=α_(l) ⁽¹⁾α_(l) ⁽²⁾ and is selected from a double codebook, e.g.C_(coef)=C_(coef) ⁽¹⁾C_(coef) ⁽²⁾, where C_(coef) ⁽¹⁾ and C_(coef) ⁽²⁾respectively are codebooks for WB and SB components of the phase. Anexample of the double phase codebook is

$C_{coph}^{(1)} = {{\left\{ {e^{j\frac{\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{7\pi}{4}}} \right\} \mspace{14mu} {and}\mspace{14mu} C_{coph}^{(2)}} = {\left\{ {e^{j\frac{\pi}{4}},e^{{- j}\frac{\pi}{4}}} \right\}.}}$

In one embodiment, the coefficient vector comprises beam selection: thethird component of the coefficient vector is B out of L beam selection,where 1≤B≤L and this selection is per SB. The coefficient vector withbeam selection matrix E_(B) can be expressed as c=E_(B)c_(B), where thelength-B coefficient vector after beam selection is c_(B)=[c₀ c₁ . . .c_(B−1)] and, for example, for 4 beams, i.e., L=4, 2L×B beam selectionmatrix E_(B) is as given in Table 7.

TABLE 7 B $\quad\begin{matrix}{{Number}\mspace{14mu} {of}\mspace{14mu} {candidate}\mspace{14mu} {beam}} \\{{selection}\mspace{14mu} {matrices}\mspace{14mu} \begin{pmatrix}4 \\B\end{pmatrix}}\end{matrix}\;$ Beam selection matrix E_(B) 1 4 E_(1,0) = e₀, E_(1,1) =e₁, E_(1,2) = e₂, E_(1,3) = e₃ 2 6 E_(2,0) = [e₀ e₁], E_(2,1) = [e₀ e₂],E_(2,2) = [e₀ e₃], E_(2,3) = [e₁ e₂], E_(2,4) = [e₁ e₃], E_(2,5) = [e₂e₃] 3 4 E_(3,0) = [e₀ e₁ e₂], E_(3,1) = [e₀ e₁ e₃] E_(3,2) = [e₀ e₂ e₃],E_(3,3) = [e₁ e₂ e₃] 4 1 E_(4,0) = [e₀ e₁ e₂ e₃]

A few alternatives for SB beam selection is as follows. In onealternative, the l value for SB beam selection is fixed inspecification, for example l=1, 2, or 4. In another alternative, the UEis configured with a single l value for SB beam selection via RRCsignaling, for example, l=1, 2, 3, or 4. In yet another alternative, theUE is configured with multiple 1 values for SB beam selection, forexample, l={1, 2, 4}, {1, 2, 3, 4}, or {2, 4}. In this example, the UEselects and reports an l value for beam selection in the CSI reportwhere this reporting is WB (hence l values do not change across SBs) orSB (hence l values can change across SBs).

In some embodiments, the UE is configured with an LC codebook whichincludes a uniform, unit-norm vector magnitude (or beam power) codebookassuming B out of L beam selection, where 1≤B≤L, and is constructedaccording to the following conditions: the minimum power level=½L, (ex:⅛ for L=4); the maximum power level=1−(B−1)/2L; the power levels areuniform with spacing ½L, (ex: ⅛ for L=4); and the sum of beam powerlevels comprising a beam power vector is one.

An example of such vector magnitude or beam power codebook is shown inTable 8 assuming B=1, 2, 3, 4 out of L=4 beams for beam selection. Notethat the number of beam power vectors is 1, 7, 21, and 35 for B=1, 2, 3,and 4, respectively. So, the total number of beam power vectors=64. Ifthe UE is configured with or reports a WB B value for beam selection,then: for B=1, the number bits to indicate a beam power vector is ┌log₂1┐=0; for B=2, the number bits to indicate a beam power vector is ┌log₂7┐=3; for B=3, the number bits to indicate a beam power vector is ┌log₂21┐=5; and for B=4, the number bits to indicate a beam power vector is┌log₂ 35┐=6.

And if the UE is configured with or reports a SB B value for beamselection, then the UE is configured with or reports a WB B value forbeam selection, then the total number of possible beam powervectors=Σ_(B=1) ⁴(_(B) ⁴)×N_(B)=1×4+6×7+4×21+1×35=165, which impliesthat the number of bits to indicated a beam power vector is ┌log₂165┐=8. The codebook for other L values such as L=8 can be constructedsimilarly.

TABLE 8 Vector magnitude codebook for L = 4 beams in total Number ofTotal number selected beams of beam power (B value) Power levels Beampower vectors m = [m₀ m₁ . . . m_(B−1)] vectors (N_(B)) 1 1 1 1 2 [7 1] [7/8 1/8], [1/8, 7/8] 7 [6 2] [6/8 2/8], [2/8 6/8] [5 3] [3/8 5/8],[5/8 3/8] [4 4] [4/8 4/8] 3 [6 1 1] [6/8, 1/8, 1/8], [1/8, 6/8, 1/8],[1/8, 1/8, 6/8] 21 [5 2 1] [5/8, 2/8, 1/8], [5/8, 1/8, 2/8], [2/8, 5/8,1/8], [2/8, 1/8, 5/8], [1/8, 5/8, 2/8], [1/8, 2/8, 5/8], [4 2 2] [4/8,2/8, 2/8], [2/8, 4/8, 2/8], [2/8, 2/8, 4/8] [4 3 1] [4/8, 3/8, 1/8],[4/8, 1/8, 3/8], [3/8, 4/8, 1/8], [1/8, 4/8, 3/8], [1/8, 4/8, 3/8],[1/8, 3/8, 4/8] [3 3 2] [3/8, 3/8, 2/8], [3/8, 2/8, 3/8], [2/8, 3/8,3/8] 4 [5 1 1 1] [5/8, 1/8, 1/8, 1/8], [1/8, 5/8, 1/8, 1/8], [1/8, 1/8,5/8, 1/8], 35 [1/8, 1/8, 1/8, 5/8] [4 2 1 1] [4/8, 2/8, 1/8, 1/8], [4/8,1/8, 2/8, 1/8], [4/8, 1/8, 1/8, 2/8] [2/8, 4/8, 1/8, 1/8], [1/8, 4/8,2/8, 1/8], [1/8, 4/8, 1/8, 2/8] [1/8, 2/8, 4/8, 1/8], [2/8, 1/8, 4/8,1/8], [1/8, 1/8, 4/8, 2/8] [1/8, 2/8, 1/8, 4/8], [1/8, 1/8, 2/8, 4/8],[2/8, 1/8, 1/8, 4/8] [3 3 1 1] [3/8, 3/8, 1/8, 1/8], [3/8, 1/8, 3/8,1/8], [3/8, 1/8, 1/8, 3/8] [1/8, 3/8, 3/8, 1/8], [1/8, 1/8, 3/8, 3/8],[1/8, 3/8, 1/8, 3/8] [3 2 2 1] [3/8, 2/8, 2/8, 1/8], [3/8, 2/8, 1/8,2/8], [3/8, 1/8, 2/8, 2/8] [2/8, 3/8, 2/8, 1/8], [2/8, 3/8, 1/8, 2/8],[2/8, 2/8, 3/8, 1/8], [2/8, 2/8, 1/8, 3/8] [2/8, 1/8, 2/8, 3/8], [2/8,1/8, 3/8, 2/8] [1/8, 3/8, 2/8, 2/8], [1/8, 2/8, 3/8, 2/8], [1/8, 2/8,2/8, 3/8] [2 2 2 2] [2/8, 2/8, 2/8, 2/8]

In some embodiments, a UE is configured with a multi-stage (at least twostages) LC codebook with at least one stage for WB components of theCSI, where WB components include at least one of the following: a beamgroup comprising of L beams; WB selection of B value for SB beamselection; WB component of co-phase values for L beams (fordual-polarized antenna arrays); WB component of LC coefficient vector(magnitude or/and phase); and at least one stage for SB components ofthe CSI, where SB components include at least one of the following: Bout of L beam selection; SB component of co-phase values for L beams(for dual-polarized antenna arrays); and SB component of LC coefficientvector (magnitude or/and phase).

In one embodiment, WB components are reported jointly using a single PMIi₁ or (i_(1,1), i_(1,2)), where the codebook for WB components can bejoint (so, one stage WB codebook) or separate (multi-stage WB codebook).In this sub-embodiment, no new CSI reporting type is needed and LTE Rel.13 Class A i₁ or (i_(1,1), i_(1,2)) can be reused.

In another embodiment, WB components are reported separately usingmultiple PMIs, where the codebook for WB components can be joint (so,one stage WB codebook) or separate (multi-stage WB codebook). In oneexample, 2 WB PMIs are reported which correspond to i₀ and i₁ or(i_(1,1), i_(1,2)), where i₁ or (i_(1,1),i_(1,2)) is used to indicate abeam group as in LTE Rel. 13 Class A codebook, and i₀ is used toindicate the rest of the WB CSI components such as WB beam power and Bvalue for beam selection. In this sub-embodiment, a new CSI reportingtype is needed to report i₀ indicating WB components other than beamgroups.

In one embodiment, SB components are reported jointly using a singlePMI, where the codebook for SB components can be joint (so, one stage SBcodebook) or separate (multi-stage SB codebook). In one example, the2^(nd) PMI i₂ of LTE Rel. 13 Class A codebook is used to report SBcomponents of LC codebook. In this example, no new CSI reporting type isneeded. In another example, a new PMI i₃ is used to indicate the SBcomponents of the LC codebook, and hence a new CSI reporting type toreport i₃ is needed.

In another embodiment, SB components are reported separately usingmultiple PMIs, where the codebook for SB components can be joint (so,one stage SB codebook) or separate (multi-stage SB codebook). In oneexample, 2 SB PMIs are reported which correspond to i₂ and i₃, where i₂is used to select B beams and B co-phase values as in LTE Rel. 13 ClassA codebook, and i₃ is used to indicate the rest of the WB CSI componentssuch as SB LC coefficients and B out L beam selection. In thissub-embodiment, a new CSI reporting type is needed to report i₃indicating SB components other than beam and co-phase selection.

FIG. 15 illustrates example periodic channel state information (CSI)reporting 1500 using a linear combination codebook according toembodiments of the present disclosure. An embodiment of the periodicchannel state information (CSI) reporting 1500 using a linearcombination codebook shown in FIG. 15 is for illustration only. One ormore of the components illustrated in FIG. 15 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

In some embodiments, a UE is configured to report PUCCH based periodicCSI, which is derived using the proposed linear combination codebook.The CSI components is divided into two subsets S1 and S2 which arereported in two different PUCCH based periodic CSI reporting instances(or subframes), as illustrated in FIG. 15. A few examples of S 1 and S2are shown in Table 9.

TABLE 9 Examples of two subsets for PUCCH based periodic CSI reportingExam- Alter- ples native CSI subset S1 CSI subset S2 0 0, 1 all WB CSIcomponents all SB CSI components 1 0 (without RI, WB beam group SBcoefficients, CQI co-phase) 2 RI, WB beam group SB beam selection, SBcoefficients, CQI 3 RI, WB beam group, WB SB coefficients, CQI beampower 4 RI, WB beam group, WB SB beam selection, SB beam powercoefficients, CQI 5 1 (with RI, WB beam group SB co-phase, SB co-phase)coefficients, CQI 6 RI, WB beam group SB beam selection, SB co-phase, SBcoefficients, CQI 7 RI, WB beam group, WB SB co-phase, SB co-phasecoefficients, CQI 8 RI, WB beam group, WB SB beam selection, SB co-phaseco-phase, SB coefficients, CQI 9 RI, WB beam group, WB SB co-phase, SBbeam power coefficients, CQI 10 RI, WB beam group, WB SB beam selection,SB beam power co-phase, SB coefficients, CQI 11 RI, WB beam group, WB SBco-phase, SB co-phase, WB beam coefficients, CQI power 12 RI, WB beamgroup, WB SB beam selection, SB co-phase, WB beam co-phase, SB powercoefficients, CQI

The UE is further configured with PUCCH Format x and y to report S1 andS2, respectively, where x and y are determined based on the number ofbits to report S1 and S2, where x and y may or may not be the same. Inone example, x=y, and S1 and S2 are reported using the same PUCCHFormat, e.g. 2 or 3. In another example, x and y can be different,belong to {2,3}, and are configured based on the associated number ofCSI bits. For instance, the UE is configured with PUCCH Format 2 if thenumber of CSI bits (associated with S1 or S2) is at most 11, and PUCCHFormat 3 if the number of CSI bits (associated with S1 or S2) is morethan 11 and at most 21.

In another example, x and y are configured based on the configuredparameters of the LC codebook. For example, if the UE is configured withB=2 (i.e., 2 beams for LC) in the LC codebook, then the UE reports S1and S2 using PUCCH Format 2 or 3 or both and if using the UE isconfigured with B=4 (i.e., 4 beams for LC) then the UE reports S1 and S2using PUCCH Format 3 only.

In yet another example, x and y are configured based on the CSIcomponents comprising S1 and S2. For instance, for Examples 1, 2, 5, and6 in Table 9, S1 is reported using PUCCH Format 2 and S2 is reportedusing PUCCH Format 3; and for Examples 3, 4, 7-12, S1 and S2 arereported using PUCCH Format 3.

In some embodiments, a UE reports the CSI derived using the proposed LCcodebook aperiodically using PUSCH only. In some embodiments, a UE isconfigured to report CSI derived using the proposed LC codebook eitherperiodically on PUCCH or aperiodically using PUSCH depending on LCcodebook parameters or CSI components comprising S1 and S2.

In one example, if B=2, then the UE is configured with either PUCCHbased periodic CSI reporting according to some embodiments of disclosureor PUSCH based aperiodic CSI reporting. However, if B=4, then onlyaperiodic CSI can be reported. In another example, if the number of CSIbits associated with S1 or S2 is within 21 bits, then the UE can beconfigured with both periodic and aperiodic CSI reporting, and if eitherone of them exceeds 21, then only aperiodic CSI reporting can beconfigured.

In some embodiments, a UE is configured to report the CSI subset S0aperiodically using PUSCH, and the CSI subsets S1 and S2 periodicallyusing PUCCH, where periodic reporting of S1 and S2 are according to someembodiments of disclosure. The UE shall derive the CSI subset S0conditioned on the last reported S1 and S2, the CSI subset S1conditioned on the last reported S0 and S2, and the CSI subset S2conditioned on the last reported S0 and S1. In one example, S0 belongsto {WB co-phase, WB beam power, B value}, S1 belongs to {RI, WB beamgroup}, and S2 belongs to {SB, beam selection, SB coefficient, SBco-phase, CQI}.

In some embodiments, a UE is configured with either LTE Rel. 13 (or anextension in LTE Rel. 14) Class A codebook or proposed linearcombination codebook to report CSI. If the UE is configured with LTERel. 13 (or an extension in LTE Rel. 14) Class A codebook, then the UEis further configured to report CSI either periodically using PUCCHFormat 2 or 3 or both; or aperiodically on PUSCH. And if the UE isconfigured with the linear combination codebook, then the UE reports thecorresponding CSI aperiodically using PUSCH only.

In some embodiments, a UE is configured with the LC codebook with L=4whose W₁ component is constructed using the LTE Rel. 13 Class A W₁codebook (corresponding beam groups are shown in FIG. 29), which areconfigured using a higher-layer RRC parameter Codebook-Config. Theresultant rank 1 and rank 2 W_(1i) codebook in this case is shown inTable 10.

TABLE 10 W₁ Codebook for 1-layer and 2-layer CSI reporting using antennaports 15 to 14 + P Value of i_(1,1) i_(1,2) Codebook- Config$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ 2 X_(2i) _(1,1) _(,2i)_(1,2)$x_{{2i_{1,1}},{2i_{1,2}}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}\mspace{25mu} v_{{{2i_{1,1}} + 1},{2i_{1,2}}}\mspace{25mu} v_{{2i_{1,1}},{{2i_{1,2}} + 1}}\mspace{20mu} v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}}} \right\rbrack}$3 i_(1,1) i_(1,2) $0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ X_(2i) _(1,1) _(,2i) _(1,2)$\quad\begin{matrix}{{x_{{2i_{1,1}},{2i_{1,2}}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}\mspace{25mu} v_{{{2i_{1,1}} + 2},{2i_{1,2}}}\mspace{25mu} v_{{2i_{1,1}},{{2i_{1,2}} + 1}}\mspace{20mu} v_{{{2i_{1,1}} + 3},{{2i_{1,2}} + 1}}} \right\rbrack}};} \\{{{if}\mspace{14mu} N_{1}} \geq N_{2}}\end{matrix}$ $\begin{matrix}{{x_{{2i_{1,1}},{2i_{1,2}}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}\mspace{25mu} v_{{2i_{1,1}} + {2i_{1,2}} + 2}\mspace{25mu} v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}}\mspace{20mu} v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 3}}} \right\rbrack}};} \\{{{if}\mspace{14mu} N_{1}} < N_{2}}\end{matrix}\quad$ 4 i_(1,1) i_(1,2)$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ X_(2i) _(1,1) _(,2i) _(1,2)$\begin{matrix}{{x_{{2i_{1,1}},{2i_{1,2}}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}\mspace{25mu} v_{{{2i_{1,1}} + 1},{2i_{1,2}}}\mspace{25mu} v_{{{2i_{1,1}} + 2},{2i_{1,2}}}\mspace{20mu} v_{{{2i_{1,1}} + 3},{2i_{1,2}}}} \right\rbrack}};} \\{{{if}\mspace{14mu} N_{1}} \geq N_{2}}\end{matrix}\quad$ $\begin{matrix}{{x_{{2i_{1,1}},{2i_{1,2}}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}\mspace{25mu} v_{{2i_{1,1}} + {2i_{1,2}} + 1}\mspace{25mu} v_{{2i_{1,1}} + {2i_{1,2}} + 2}\mspace{20mu} v_{{2i_{1,1}} + {2i_{1,2}} + 3}} \right\rbrack}};} \\{{{if}\mspace{14mu} N_{1}} < N_{2}}\end{matrix}\quad$

In some embodiments, the norm of a length-N vector v=[v₀ v₁ . . .v_(N−1)]^(T) is defined as

${{v} = \sqrt{\sum\limits_{i = 0}^{N - 1}{v_{i}}^{2}}},$

where |v_(i)| is the absolute value or magnitude of the i-th componentof vector v.

In one embodiment 0, the UE is configured with an LC codebook with Basis0 where rank 1 and rank 2 pre-coders are given according to at least oneof the following sub-embodiments (Sub-embodiment 0-0 to 0-5).

In sub-embodiment 0-0, the rank 1 and rank 2 LC pre-coders without beamselection are given by:

${W_{l,m,k}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}w_{l,m,k}^{( + )} \\w_{l,m,k}^{( - )}\end{bmatrix}}},{W_{l,m,k}^{(2)} = {\frac{1}{2}\begin{bmatrix}w_{l,m,k}^{( + )} & w_{l,m,k}^{( + )} \\w_{l,m,k}^{( - )} & {- w_{l,m,k}^{( - )}}\end{bmatrix}}}$${{{Where}\mspace{14mu} w_{l,m,k}^{( + )}} = \frac{x_{l,m}c_{k}^{( + )}}{{x_{l,m}c_{k}^{( - )}}}};$${w_{l,m,k}^{( - )} = \frac{x_{l,m}c_{k}^{( - )}}{{x_{l,m}c_{k}^{( - )}}}};$

x_(l,m) is a beam group (comprising of L beams) selected from acodebook, an example of which is Table 10 for L=4; c_(k) ⁽⁺⁾=[c_(k,0)c_(k,1) . . . c_(k,L−1)]^(T) is a length-2L coefficient vector, selectedfrom a coefficient codebook proposed earlier in the present disclosure,which is decomposed into two parts c_(k) ⁽⁺⁾=[c_(k,0) c_(k,1) . . .c_(k,L−1)]^(T) and c_(k) ⁽⁻⁾=[c_(k,L) c_(k,L+1) . . . c_(k,2L−1)]^(T)for the two polarizations (+45 and −45) of antenna ports.

In Sub-embodiment 0-1, the rank 1 and rank 2 LC pre-coders with B out ofL beam selection, where 1≤B≤L, are given by:

${W_{l,m,b,k}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}w_{l,m,b,k}^{( + )} \\w_{l,m,b,k}^{( - )}\end{bmatrix}}},{W_{l,m,b,k}^{(2)} = {\frac{1}{2}\begin{bmatrix}w_{l,m,b,k}^{( + )} & w_{l,m,b,k}^{( + )} \\w_{l,m,b,k}^{( - )} & {- w_{l,m,b,k}^{( - )}}\end{bmatrix}}}$${{{Where}\mspace{14mu} w_{l,m,b,k}^{( + )}} = \frac{x_{l,m}E_{B,b}c_{k}^{( + )}}{{x_{l,m}E_{B,b}c_{k}^{( + )}}}};$${w_{l,m,b,k}^{( - )} = \frac{x_{l,m}E_{B,b}c_{k}^{( - )}}{{x_{l,m}E_{B,b}c_{k}^{( - )}}}};$

x_(l,m) is a beam group (comprising of L beams), selected from acodebook, an example of which is Table 10 for L=4; E_(B),b is the beamselection matrix, an example of which is Table 7 for L=4; c_(k)=[c_(k,0)c_(k,1) . . . c_(k,2B−1)]^(T) is a length-2B coefficient vector,selected from a coefficient codebook proposed earlier in the presentdisclosure, which is decomposed into two parts c_(k) ⁽⁺⁾=[c_(k,0)c_(k,1) . . . c_(k,B−1)]^(T) and c_(k) ⁽⁻⁾=[c_(k,B) c_(k,B+1) . . .c_(k,2B−1)]^(T), for the two polarizations (+45 and −45) of antennaports.

In Sub-embodiment 0-2, the rank 1 and rank 2 LC pre-coders are derivedwithout beam selection and with a common co-phase for all beams, and aregiven by:

$W_{l,m,n,k}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}w_{l,m,k} \\{\phi_{n}w_{l,m,k}}\end{bmatrix}}$ $W_{l,m,n,k}^{(2)} = {\frac{1}{2}\begin{bmatrix}w_{l,m,k} & w_{l,m,k} \\{\phi_{n}w_{l,m,k}} & {{- \phi_{n}}w_{l,m,k}}\end{bmatrix}}$${{{where}\mspace{14mu} w_{l,m,k}} = \frac{x_{l,m}c_{k}}{{x_{l,m}c_{k}}}};$

x_(l,m) is a beam group (comprising of L beams), selected from acodebook, an example of which is Table 10 for L=4; φ_(n) is a co-phasevalue that is selected from a co-phase codebook proposed earlier in thepresent disclosure; and c_(k)=[c_(k,0) c_(k,1) . . . c_(k,L−1)]^(T) is alength-L coefficient vector, selected from a coefficient codebookproposed earlier in the present disclosure.

In Sub-embodiment 0-3, the rank 1 and rank 2 LC pre-coders are derivedwith B out of L beam selection, where 1≤B≤L, and with a common co-phasefor all beams, and are given by:

$W_{l,m,b,n,k}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}w_{l,m,b,k} \\{\phi_{n}w_{l,m,b,k}}\end{bmatrix}}$ $W_{l,m,b,n,k}^{(2)} = {\frac{1}{2}\begin{bmatrix}w_{l,m,b,k} & w_{l,m,b,k} \\{\phi_{n}w_{l,m,b,k}} & {{- \phi_{n}}w_{l,m,b,k}}\end{bmatrix}}$${{{where}\mspace{14mu} w_{l,m,b,k}} = \frac{x_{l,m}E_{B,b}c_{k}}{{x_{l,m}E_{B,b}c_{k}}}};$

x_(l,m) is a beam group (comprising of L beams), selected from acodebook, an example of which is Table 10 for L=4; E_(B,b) is the beamselection matrix, an example of which is Table 7 for L=4; φ_(n) is aco-phase value that is selected from a co-phase codebook proposedearlier in the present disclosure; and c_(k)=[c_(k,0) c_(k,1) . . .c_(k,L−1)]^(T) is a length-L coefficient vector, selected from acoefficient codebook proposed earlier in the present disclosure.

In Sub-embodiment 0-4, the rank 1 and rank 2 LC pre-coders are derivedwithout beam selection and with different co-phase for all beams, andare given by:

${W_{l,m,n,k}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}w_{l,m,k}^{( + )} \\w_{l,m,n,k}^{( - )}\end{bmatrix}}},{W_{l,m,n,k}^{(2)} = {\frac{1}{2}\begin{bmatrix}w_{l,m,k}^{( + )} & w_{l,m,k}^{( + )} \\w_{l,m,n,k}^{( - )} & {- w_{l,m,n,k}^{( - )}}\end{bmatrix}}}$${{{where}\mspace{14mu} w_{l,m,k}^{( + )}} = \frac{x_{l,m}c_{k}}{{x_{l,m}c_{k}}}};$${w_{l,m,n,k}^{( - )} = \frac{x_{l,m}\varphi_{n}c_{k}}{{x_{l,m}\varphi_{n}c_{k}}}};$

x_(l,m) is a beam group (comprising of L beams), selected from acodebook, an example of which is Table 7 for L=4; ϕ_(n)=diag(φ_(n,0),φ_(n,1), . . . , φ_(n,L−1)) is a diagonal matrix with co-phase valuesφ_(n,0), φ_(n,1), . . . , φ_(n,L−1) at the diagonal entries that areselected from a co-phase codebook proposed earlier in the aforementionedembodiments. c_(k)=[c_(k,0) c_(k,1) . . . c_(k,L−1)]^(T) is a length-Lcoefficient vector, selected from a coefficient codebook proposedearlier in the present disclosure.

In Sub-embodiment 0-5, the rank 1 and rank 2 LC pre-coders are derivedwith B out of L beam selection, where 1≤B≤L, and with different co-phasefor all beams, and are given by:

${W_{l,m,b,n,k}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}w_{l,m,b,k}^{( + )} \\w_{l,m,b,n,k}^{( - )}\end{bmatrix}}},{W_{l,m,b,n,k}^{(2)} = {\frac{1}{2}\begin{bmatrix}w_{l,m,b,k}^{( + )} & w_{l,m,b,k}^{( + )} \\w_{l,m,b,n,k}^{( - )} & {- w_{l,m,b,n,k}^{( - )}}\end{bmatrix}}}$${{{where}\mspace{14mu} w_{l,m,b,k}^{( + )}} = \frac{x_{l,m}E_{B,b}c_{k}}{{x_{l,m}E_{B,b}c_{k}}}};$${w_{l,m,b,n,k}^{( - )} = \frac{x_{l,m}E_{B,b}\varphi_{n}c_{k}}{{x_{l,m}E_{B,b}\varphi_{n}c_{k}}}};$

x_(l,m) is a beam group (comprising of L beams), selected from acodebook, an example of which is Table 10 for L=4; E_(B,b) is the beamselection matrix, an example of which is Table 7 for L=4;ϕ_(n)=diag(φ_(n,0), φ_(n,1), . . . , φ_(n,B−1)) is a diagonal matrixwith co-phase values φ_(n,0), φ_(n,1), . . . , φ_(n,B−1) at the diagonalentries that are selected from a co-phase codebook proposed earlier inthe present disclosure. c_(k)=[c_(k,0) c_(k,1) . . . c_(k,B−1)]^(T) is alength-B coefficient vector, selected from a coefficient codebookproposed earlier in the present disclosure.

In one embodiment 1, the UE is configured with an LC codebook with Basis1 where rank 1 and rank 2 pre-coders are given according to at least oneof Sub-embodiments 1-0 to 1-5, which are similar to Sub-embodiments 0-0to 0-5 with replacing x_(l,m) with y_(l,m,p)=x_(l,m)M_(p), and replacingsubscripts (l, m, . . . ) in rank 1 and rank 2 pre-coders W_(l,m, . . .)⁽¹⁾ and W_(l,m, . . .) ⁽²⁾ with (l, m, p, . . . ) to obtainW_(l,m,p, . . .) ⁽¹⁾, . . . W_(l,m,p, . . .) ⁽²⁾ whereM_(n)=diag(m_(n,0) ⁽¹⁾ m_(n,1) ⁽¹⁾ . . . m_(n,L−1) ⁽¹⁾) is WB magnitudeor power levels of L beams. Note that, in this case, WB beam magnitudeor power level (p index) is explicitly reported, for example, using anew WB PMI i₀ for beam power.

In an alternative Embodiment 1, the WB beam magnitude or power level (pindex) is implicitly merged with (l, m) or l or m and is reported with(i_(1,1), i_(1,2)) or i_(1,1) or i_(1,2). In this alternative, thepre-coder expressions remain the same as in Sub-embodiments 0-0 to 0-5.

In one embodiment 2, the UE is configured with an LC codebook with Basis2 where rank 1 and rank 2 pre-coders are given according to at least oneof Sub-embodiments 2-2 to 2-5, which are similar to Sub-embodiments 0-2to 0-5 with replacing x_(l,m) with y_(l,m,n)=x_(l,m)ϕ_(n), and replacingsubscripts (l, m, . . . ) in rank 1 and rank 2 pre-coders W_(l,m, . . .)⁽¹⁾ and W_(l,m, . . .) ⁽²⁾ with (l, m, p, . . . ) to obtainW_(l,m, p, . . .) ⁽¹⁾ and W_(l,m, p, . . .) ⁽²⁾ where ϕ_(n)=diag(1 1 . .. 1) is WB co-phase values for +45 polarizations, and ϕ_(n)=diag(φ_(n,0)φ_(n,1) . . . φ_(n,L−1)) is WB co-phase for −45 polarizations. Notethat, in this case, WB co-phase values are explicitly reported, forexample, using a new WB PMI i₀ for WB co-phase values.

In an alternative Embodiment 2, the WB co-phase values are implicitlymerged with (l, m) or l or m and are reported with (i_(1,1), i_(1,2)) ori_(1,1) or i_(1,2). In this alternative, the pre-coder expressionsremain the same as in Sub-embodiments 0-2 to 0-5.

In one embodiment 3, the UE is configured with an LC codebook with Basis3 where rank 1 and rank 2 pre-coders are given according to at least oneof Sub-embodiments 3-2 to 3-5, which are similar to Sub-embodiments 0-2to 0-5 with replacing x_(l,m) with y_(l,m,p,n)=x_(l,m)M_(p)ϕ_(n), andreplacing subscripts (l, m, . . . ) in rank 1 and rank 2 pre-codersW_(l,m, . . .) ⁽¹⁾ and W_(l,m, . . .) ⁽²⁾ with (l, m, p, n, . . . ) toobtain W_(l,m,p,n, . . .) ⁽¹⁾ and W_(l,m,p,n, . . .) ⁽²⁾ whereM_(n)=diag(m_(n,0) ⁽¹⁾ m_(n,1) ⁽¹⁾ . . . m_(n,L−1) ⁽¹⁾) is WB magnitudeor power levels of L beams, and ϕ_(n)=diag(1 1 . . . 1) is WB co-phasevalues for +45 polarizations, and ϕ_(n)=diag(φ_(n,0) φ_(n,1) . . .φ_(n,L−1)) is WB co-phase for −45 polarizations.

In some embodiments, a UE is configured with either Class A codebookbased CSI feedback (for low spatial resolution feedback) or LC codebookbased CSI feedback (for high spatial resolution feedback) (via RRCsignaling using parameter LCCodebookEnabled) based on a dual-stagecodebook structure W=W₁W₂. In such embodiments, W₁ codebook for the twotypes of CSI feedback is according to one of the following alternatives:In one example of common W₁, the W₁ codebook is common between Class Aand LC codebooks. In another example of different W₁, the W₁ codebookfor Class A codebook is different from that for LC codebook. In yetanother example of subset W₁, the W₁ codebook for Class A codebook is asubset of that for LC codebook.

FIG. 16 illustrates an example W1 codebook 1600 according to embodimentsof the present disclosure. An embodiment of the W1 codebook 1600 shownin FIG. 16 is for illustration only. One or more of the componentsillustrated in FIG. 16 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

An illustration of the three W₁ codebook alternatives is shown in FIG.12, where the W₁ codebook is according to some embodiments ofdisclosure, for example, LTE Rel. 13 Class A W₁ codebook (e.g, Table 10)or a new W₁ codebook proposed in the present disclosure.

The W₂ codebook for Class A codebook is according to LTE Rel. 13 (or anextension in LTE Rel. 14) Class A W₂ codebook. Alternatively, a new W₂codebook is considered. The W₂ codebook for LC codebook is according tosome embodiments of disclosure. In addition, a new W₂ codebook may ormay not include the W₂ codebook of Class A codebook.

In one embodiment, the LTE Rel. 13 Class A codebook parameterCodebook-Config is used to configure Class A or LC codebook. Forexample, when Codebook-Config=1, then the UE is configured with Class Acodebook, and Codebook-Config=2, 3, 4, then the UE is configured with LCcodebook. This is an example of different W₁ codebook for Class A and LCcodebooks. In another embodiment, a new RRC parameter such asLCCodebookEnabled is used to configure Class A or LC codebook accordingto the previous embodiment.

In such embodiments, all three alternatives of W₁ codebook are possible.In one example of common W₁, LTE Rel. 13 Class A W₁ codebook forCodebook-Config=2, 3, or 4 is used regardless of the configured CSI type(e.g., LCCodebookEnabled is turned ON or OFF). In another example ofdifferent W₁, LTE Rel. 13 Class A W₁ codebook for Codebook-Config=2, 3,or 4 is used if Class A codebook is configured (e.g., LCCodebookEnabledis turned OFF), and a new W₁ codebook is used if LC codebook isconfigured (e.g., LCCodebookEnabled is turned ON). In yet anotherexample of subset W₁, LTE Rel. 13 Class A W₁ codebook forCodebook-Config=2, 3, or 4 is used if Class A codebook is configured(e.g., LCCodebookEnabled is turned OFF), and a new W₁ codebook whichincludes LTE Rel. 13 Class A W₁ codebook is used if LC codebook isconfigured (e.g., LCCodebookEnabled is turned ON).

FIG. 17 illustrates example master beam groups 1700 according toembodiments of the present disclosure. An embodiment of the master beamgroups 1700 shown in FIG. 17 is for illustration only. One or more ofthe components illustrated in FIG. 17 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, a UE is configured with an oversampled DFT codebookas the master basis set comprising of O₁N₁×O₂N₂ DFT beams and (L₁, L₂)parameters representing the number of beams in the two dimensions of themaster beam group.

The UE is further configured with multiple types of master beam groupsbased on the spacing (p₁, p₂) between two adjacent beams in twodimensions of the master beam group. The UE reports one of multipletypes of master beam groups in the UE's CSI report where this reportingcan be explicit as a new WB CSI feedback component or it is implicitwith either i₁ or (i_(1,1), i_(1,2)). An illustration of two types ofmaster beam groups is shown in FIG. 22, where each small squarerepresents a 2D DFT beam. When (p₁, p₂)=(1, 1), the master beam groupcorresponds to L₁L₂ closely spaced beams, and when (p₁, p₂)=(O₁, O₂),the master beam group corresponds to L₁L₂ orthogonal beams. Threeexamples of master beam groups for each type are also shown as BG0, BG1,and BG2.

Alternatively, eNB configures one of multiple types of master beamgroups via RRC signaling. For example, eNB configures one of the twomaster beam groups shown in FIG. 17 via 1-bit RRC parameterMasteBeamGroupType.

The components of the LC codebook (assuming Basis 0) are constructed asfollows. In one example, a master beam group of configured or reportedtype is reported as the 1st PMI i₁ or (i_(1,1), i_(1,2)). This reportingis WB. The range of values of i_(1,1) and i_(1,2) is given by i_(1,1)=0,1, 2, . . . O₁N₁/s₁ and i_(1,2)=0, 1, 2, . . . O₂N₂/s₂, where (s₁,s₂)are spacing between two adjacent master beam groups in two dimensions.The example values of s₁ (or s₂) are 1, 2, O₁/4 (or O₂/4), O₁/2 (orO₂/2), and O₁ (or O₂). So, the number of bits to report i_(1,1) andi_(1,2) is

${\log_{2}\left\lceil \frac{O_{1}N_{1}}{s_{1}} \right\rceil {\mspace{11mu} \;}{and}\mspace{14mu} \log_{2}\left\lceil \frac{O_{2}N_{2}}{s_{2}} \right\rceil},$

respectively. In another example, for each SB in which the UE isconfigured to report PMI/CQI, the UE reports at least one of thefollowing.

In one embodiment of beam selection, L out of L₁L₂ beams are selectedfrom the reported master beam group. Examples of L values are 1, 2, 4,and 8. The L value can be reported in the CSI report or The L value isconfigured via higher layer RRC signaling. In the case of the former,the reported L value is either WB or SB. Two alternatives for thisselection are as follows. In one alternative of parameterized, theselection of L beams is based on Config parameter. Examples of a fewbeam selections are shown in FIG. 18. In one example, the UE reports apreferred Config value in per SB CSI report where the set of possibleConfig values is fixed, for example Config 0-16 in FIG. 18. In anotherexample, the UE reports a WB L value and a Config value per SBcorresponding to the reported L. For example, the UE reports L=2 in theWB CSI report (2-bit WB reporting of an L value) and reports one ofConfig 0-Config 3 in per SB CSI report (2-bit SB reporting on Config).Alternatively, an L value is configured via RRC signaling and the UEreports a Config value corresponding to the reported L. In yet anothermethod, the set of Config values for per SB beam selection is configuredvia RRC signaling. For example, a length 17 bitmap is used to configurethe set of Config values (e.g., FIG. 18).

FIG. 18 illustrates an example beam selection 1800 according toembodiments of the present disclosure. An embodiment of the beamselection 1800 shown in FIG. 18 is for illustration only. One or more ofthe components illustrated in FIG. 18 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In another embodiment of unconstrained, the selected L beams isunconstrained and any L out of L₁L₂ beams can be reported. In this case,the reporting can be based on a bitmap of length L₁L₂. In one example ofco-phase, co-phase values (for two polarizations) for L selected beamsare selected using a co-phase codebook proposed in some embodiments ofthe present disclosure. In another example of coefficients, coefficientsto linearly combine L selected beams are selected using a coefficientcodebook proposed in some embodiments of disclosure. As alternativecoefficient codebooks, other codebooks such as Householder andGrassmanian codebooks can also be considered.

In another embodiment, the UE is configured with a DFT codebook withoutoversampling (e.g. oversampling factor=1). As in the previousembodiment, the UE reports a master beam group comprises of L₁L₂ beams(WB) and for each SB, reports L out of L₁L₂ reported beams. In addition,the UE also reports the rotation matrix (M) for either each of L beams(L rotation matrices) or the whole beam group (one rotation matrix),where the rotation can be WB or SB, and the rotation can be only in onedimension or in both dimensions. An example of rotation matrix is adiagonal matrix whose diagonal entries form a DFT vector.

In some embodiments, the UE is configured with an LC codebook whose W₁beam groups depend on the configured or reported L value. For example,if L=1, then W₁ beam groups are the same as that in LTE Rel. 13 (or anextension in LTE Rel. 14) Class A codebook. And if L>1 (e.g. L=2, 4, 8),then W₁ beam groups are different from that in LTE Rel. 13 (or anextension in LTE Rel. 14) Class A codebook.

In some embodiments, the UE is configured with a beam spacing parameterpair (p₁, p₂) whose value depends on the RRC parameter LCCodebookEnabledto configure LC codebook according to some embodiments of disclosure. IfLCCodebookEnabled is turned OFF (i.e. Class A codebook is configured),then p_(d), where d=1, 2 can take values from {1, 2}, and ifLCCodebookEnabled is turned ON (i.e. LC codebook is configured), thenp_(d), where d=1, 2 can take values from {1, O_(d)}.

In some embodiments, the UE is configured with a beam spacing parameterpair (p₁, p₂) for Class A or LC codebook that is applicable up to afixed rank r, e.g. r=2. For rank>r, beam spacing is fixed (hence doesnot need to be configured), for example to that for rank>r Class Acodebook.

In some embodiments, the UE is configured with a beam spacing parameterpair (p₁, p₂) for Class A or LC codebook depending on rank r. In oneexample, the beam spacing is as follows: for r=1-2, p_(d), where d=1, 2can take values from {1,2}; for r=3-4, p_(d), where d=1, 2 can takevalues from {O_(d)/4, O_(d)/2}; and for r=5-8, p_(d), where d=1, 2 cantake values from {O_(d)}. In another example, the beam spacing is asfollows: for r=1-2, p_(d), where d=1, 2 can take values from {1,2}; andfor r=3-8, p_(d), where d=1, 2 can take values from {O_(d)}.

In some embodiments, the UE is configured with LTE Rel. 13 Class A W1codebook (that represents beam groups) for Codebook-Config 2, 3, 4 asthe W1 codebook for the linear combination codebook proposed indisclosure. The W1 beam groups in LTE Rel. 13 Class A codebook for rank1-8 and Codebook-Config 2, 3, 4 are shown in FIG. 19. There are threepossible beam group configurations for LC codebook. In one example ofconfiguration 0, this configuration corresponds to rank 1-2 Class A W1codebook. There are four beams shown in black squares that form a beamgroup depending on the Codebook-Config parameter. In another example ofconfiguration 1, this configuration corresponds to rank 3-4 Class A W1codebook. There are eight beams (4 orthogonal beam pairs) shown in blacksquares that form a beam group depending on the Codebook-Configparameter. Also, there are two possible orthogonal beam direction for 2Dport layouts (3 for 1D port layouts) that are shown as k=0 and 1. Ifk=0, 4 beams are location at (0, 0) and 4 beams are location at (O₁, 0),and if k=1, 4 beams are location at (0, 0) and 4 beams are location at(0, 02). One k value is reported by the UE jointly with i_(1,1). In yetanother example of configuration 2, this configuration corresponds torank 7-8 Class A W1 codebook. There are four (orthogonal) beams shown inblack squares that form a beam group depending on the Codebook-Configparameter.

Note that orthogonal beam group for rank 5-6 Class A W1 codebook (whichhas 3 orthogonal beams included in rank 7-8 Class A W1 beam group) isnot shown here. The embodiment, however, is applicable to rank 5-6 ClassA W1 codebook also.

FIG. 19 illustrates an example class A W1 beam groups 1900 for rank 1-8and codebook-configuration 2, 3, and 4 according to embodiments of thepresent disclosure. An embodiment of the class A W1 beam groups 1900 forrank 1-8 and codebook-configuration 2, 3, and 4 shown in FIG. 19 is forillustration only. One or more of the components illustrated in FIG. 19can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure. A few example of W1 codebook configurationfor LC codebook is as follows. In one example, the rank r W1 codebookfor LC codebook is the same as rank r W1 codebook for Class A codebook,where r can be 1-8 for example. In another example, the rank 1-2 W1codebook for LC codebook is the same as rank 1-2 W1 codebook for Class Acodebook, and the rank r>2 W1 codebook for LC codebook is the same asrank 7-8 W1 codebook for Class A codebook. In yet another example, therank r W1 codebook for LC codebook, where r can be 1-8 for example, isthe same as rank 7-8 W1 codebook for Class A codebook.

In some embodiments, a UE is configured with three separate rank 1 andrank 2 LC codebook tables for Codebook-Config=2, 3, and 4, an example ofrank 1 codebook table is shown in Table 11.

TABLE 11 Codebook for 1-layer CSI reporting using antenna ports 15 to14 + P Value of i₂ Codebook- i_(1,1) i_(1,2) 0 1 Config 2$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(,0,0) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,0,1) ⁽¹⁾ i_(1,1) i_(1,2) 2 3$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(,0,2) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,0,3) ⁽¹⁾ Pre-coders for i₂ ≥4 are contructed similarly. Value of i₂ Codebook- i_(1,1) i_(1,2) 0 1Config 3 $0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(,0,0) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,0,1) ⁽¹⁾ i_(1,1) i_(1,2) 2 3$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(,0,2) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,0,3) ⁽¹⁾ Pre-coders for i₂ ≥4 are contructed similarly. Value of i₂ Codebook- i_(1,1) i_(1,2) 0 1Config 4 $0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(,0,0) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,0,1) ⁽¹⁾ i_(1,1) i_(1,2) 2 3$0,1,\ldots \;,{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \;,{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1) _(,2i) _(1,2)_(,0,2) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,0,3) ⁽¹⁾ Pre-coders for i₂ ≥4 are contructed similarly.

In some embodiments, a UE is configured with a single rank 1 and rank 2LC codebook tables for Codebook-Config=2, 3, and 4 in which W1 (fori_(1,1), i_(1,2)) and W2 (for i₂) components of the codebook are in thesame table, an example of rank 1 codebook table is shown in Table 12.

TABLE 12 Codebook for 1-layer CSI reporting using antenna ports 15 to14 + P Value of Codebook- i₂ Config i_(1,1) i_(1,2) 0 1 2,3,4$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1)_(,2i) _(1,2) _(,0,0) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,0,1) ⁽¹⁾i_(1,1) i_(1,2) 2 3$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ W_(2i) _(1,1)_(,2i) _(1,2) _(,0,2) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,0,3) ⁽¹⁾Pre-coders for i₂ ≥ 4 are contructed similarly.

In some embodiments, a UE is configured with a single rank 1 and rank 2LC codebook tables for Codebook-Config=2, 3, and 4 in which W1 (fori_(1,1), i_(1,2)) and W2 (for i₂) components of the codebooks areseparated into two codebook tables (one for beam group and the other forLC coefficients with or without co-phase or/and magnitude), an exampleof such rank 1 codebook table is Table 10 for W1 (corresponding PMI isLTE Rel. 13 Class A PMI i_(1,1), i_(1,2)) and Table 13 for W2(corresponding PMI is LTE Rel. 13 Class PMI i₂ indicating LCcoefficients) or W3 (corresponding PMI is a new PMI i₃ for LCcoefficients).

TABLE 13 W2 or W3 Codebook for 1-layer CSI reporting using antenna ports15 to 14 + P i₂ or i₃ 0 1 2 3 W_(2i) _(1, 1) _(, 2i) _(1, 2) _(, 0, 0)⁽¹⁾ W_(2i) _(1, 1) _(, 2i) _(1, 2) _(, 0, 1) ⁽¹⁾ W_(2i) _(1, 1) _(, 2i)_(1, 2) _(, 0, 2) ⁽¹⁾ W_(2i) _(1, 1) _(, 2i) _(1, 2) _(, 0, 3) ⁽¹⁾Pre-coders for i₂ ≥ 4 are contructed similarly.

In some embodiments, a UE is configured with rank 1 and rank 2 W2 LCcodebook tables in which the second PMI i₂ has two components (i_(2,1),i_(2,2)). The 1st component i_(2,1) indicates LC coefficient vector and2nd component i_(2,2) indicates co-phase for the two polarizations.Alternatively, the 1st component i_(2,1) indicates co-phase for the twopolarizations and 2nd component i_(2,2) indicates LC coefficient vector.An example of such rank 1 W2 codebook table is shown in Table 14.

In one embodiment, i_(2,1) and i_(2,2) are reported separately as twocomponents of the 2nd PMI. In another embodiment, i_(2,1) and i_(2,2)are reported jointly as a single second PMI. In this later case, theleast significant bits (LSB) (e.g. 2 bits for rank 1 and 1 bit for rank2 from right)) of i₂ correspond to i_(2,2)(co-phase), and the mostsignificant bits (MSB) (e.g. 6 bits of from left) of i₂ correspond toi_(2,1) (coefficients). Alternatively, the LSB (e.g. 6 bits of fromleft) of i₂ correspond to i_(2,1) (coefficients) and the MSB (e.g. 2bits for rank 1 and 1 bit for rank 2 from right)) of i₂ correspond toi_(2,2)(co-phase).

TABLE 14 W2 Codebook for 1-layer CSI reporting using antenna ports 15 to14 + P i_(2, 2) i_(2, 1) 0 1 2 3 0, 1, . . . , 63 W_(2i) _(1, 1) _(, 2i)_(1, 2) _(, i) _(2, 1) _(, 0) ⁽¹⁾ W_(2i) _(1, 1) _(, 2i) _(1, 2) _(, i)_(2, 1) _(, 1) ⁽¹⁾ W_(2i) _(1, 1) _(, 2i) _(1, 2) _(, i) _(2, 1) _(, 2)⁽¹⁾ W_(2i) _(1, 1) _(, 2i) _(1, 2) _(, i) _(2, 1) _(, 3) ⁽¹⁾ Pre-codersfor i_(2, 2) ≥ 4 are contructed similarly.

In some embodiments, i_(2,1) and i_(2,2) respectively are represented asi₂ and i₃, where i₂ is LTE Rel. 13 Class A 2^(nd) PMI and i₃ is a newPMI for LC codebook.

In some embodiments, a UE is configured with a single rank 1 and rank 2LC codebook tables for Codebook-Config=2, 3, and 4 in which there arethree codebook (three-stage) tables: W1 codebook table for beam groupscomprising of L (or B) beams; W2 or W21 codebook table for co-phasevalues for the two polarizations and L (or B) beams; and W3 or W22codebook table for LC coefficients. An example of W1 codebook table isTable 10 and the LTE Rel. 13 Class A PMI i_(1,1), i_(1,2) is used toindicate a beam group in W1 codebook.

An example of W2 or W21 co-phase codebook and B out of L=4 beamselection assuming QPSK co-phase is shown in Table 15. There are twoalternatives for B value for SB beam selection. In one embodiment of Alt0 (WB): a single B value is selected WB and hence does not change acrossSBs. For example, if B=2, then the B value remains the same in all SBs(i.e., the number of beams for LC is 2 in all SBs). In anotherembodiment of Alt 1 (SB): a single B value is selected per SB and hencecan change across SBs. For example, in one SB, B can be 2 (i.e., thenumber of beams for LC is 2 in one SB), and in another SB, B can be 4(i.e., the number of beams for LC is 4 in another SB). The otherco-phase codebooks (for example double co-phase codebook) mentioned indisclosure can be constructed similarly.

An example of W3 or W22 coefficient codebook and B out of L=4 beamselection assuming QPSK coefficients is shown in Table 16. Similar toco-phase, there are two alternatives for B value for SB beam selection.The other coefficient codebooks (for example double coefficient codebookand DFT coefficient codebook) mentioned in disclosure can be constructedsimilarly.

TABLE 15 W2 or W21 co-phase codebook (QPSK co-phase) Co-phase vectorOffset n_(b), b = B B value type PMI (i₂ or i₂₁) (y) 0, ... , B − 1Co-phase vector 1 Alt 0: WB Alt 1: SB  0-3  0-3   0  0$\left\lfloor {\frac{i_{2} - y}{4^{B - b}}\mspace{14mu} {mod}\mspace{14mu} 4} \right\rfloor$$e^{\frac{j\; 2\; \pi \; n_{0}}{4}}$ 2 Alt 0: WB Alt 1: SB  0-154-19  0  4$\left\lbrack {e^{\frac{j\; 2\pi \; n_{0}}{4}},e^{\frac{j\; 2\; \pi \; n_{1}}{4}}} \right\rbrack$3 Alt 0: WB Alt 1: SB  0-63 20-83   0 20$\left\lbrack {e^{\frac{j\; 2\pi \; n_{0}}{4}},e^{\frac{j\; 2\; \pi \; n_{1}}{4}},e^{\frac{j\; 2\; \pi \; n_{2}}{4}}} \right\rbrack$4 Alt 0: WB Alt 1: SB   0-255 84-339  0 84$\left\lbrack {e^{\frac{j\; 2\pi \; n_{0}}{4}},e^{\frac{j\; 2\; \pi \; n_{1}}{4}},e^{\frac{j\; 2\; \pi \; n_{2}}{4}},e^{\frac{j\; 2\; \pi \; n_{3}}{4}}} \right\rbrack$

TABLE 16 W3 or W22 coefficient codebook (QPSK coefficients) Coefficientvector PMI Offset B B value type (i₃ or i₂₂) (z) k_(b), b = 1, ... , B −1 Coefficient vector 2 Alt 0: WB Alt 1: SB  0-3 0-3  0  0$\left\lfloor {\frac{i_{3} - z}{4^{B - b - 1}}\mspace{14mu} {mod}\mspace{14mu} 4} \right\rfloor$$\left\lbrack {1,e^{\frac{j\; 2\; \pi \; k_{1}}{4}}} \right\rbrack$3 Alt 0: WB Alt 1: SB   0-15  4-19  0  4$\left\lbrack {1,e^{\frac{j\; 2\pi \; k_{1}}{4}},e^{\frac{j\; 2\; \pi \; k_{2}}{4}}} \right\rbrack$4 Alt 0: WB Alt 1: SB   0-63 20-83  0 20$\left\lbrack {1,e^{\frac{j\; 2\pi \; k_{1}}{4}},e^{\frac{j\; 2\; \pi \; k_{2}}{4}},e^{\frac{j\; 2\; \pi \; k_{3}}{4}}} \right\rbrack$

In some embodiments, the UE is configured with an LC codebook for rank 1and rank 2 in which LTE Rel. 13 Class A codebook table for rank 1 isused to select L=4 beams with co-phase values depending inCodebook-Config=2, 3, 4. An example of such a codebook (W2 or W21codebook) for rank 1 is shown in Table 17. The corresponding PMI is i₂or i_(2,1). The selected L=4 beams with co-phase are then combined usinganother codebook (W3 or W22 codebook) Table 18. The corresponding PMI isi₃ or i_(2,2), which is reported as a new CSI reporting type.

The LC codebook for SB beam selection of B out of L=4 beams can beconstructed similarly.

TABLE 17 W2 or W21 Codebook for 1-layer CSI reporting using antennaports 15 to 14 + P i₂ or i_(2,1) 0 1 2 3 y_(2i,) _(1,1) _(2i) _(1,2)_(,0) ⁽¹⁾ y_(2i,) _(1,1) _(2i) _(1,2) _(,1) ⁽¹⁾ y_(2i,) _(1,1) _(2i)_(1,2) _(,2) ⁽¹⁾ y_(2i,) _(1,1) _(2i) _(1,2) _(,3) ⁽¹⁾ 4 5 6 7 y_(2i,)_(1,1) _(2i) _(1,2) _(,4) ⁽¹⁾ y_(2i,) _(1,1) _(2i) _(1,2) _(,5) ⁽¹⁾y_(2i,) _(1,1) _(2i) _(1,2) _(,6) ⁽¹⁾ y_(2i,) _(1,1) _(2i) _(1,2) _(,7)⁽¹⁾ 8 9 10 11 y_(2i,) _(1,1) _(2i) _(1,2) _(,8) ⁽¹⁾ y_(2i,) _(1,1) _(2i)_(1,2) _(,9) ⁽¹⁾ y_(2i,) _(1,1) _(2i) _(1,2) _(,10) ⁽¹⁾ y_(2i,) _(1,1)_(2i) _(1,2) _(,11) ⁽¹⁾ 12 13 14 15 y_(2i,) _(1,1) _(2i) _(1,2) _(,12)⁽¹⁾ y_(2i,) _(1,1) _(2i) _(1,2) _(,13) ⁽¹⁾ y_(2i,) _(1,1) _(2i) _(1,2)_(,14) ⁽¹⁾ y_(2i,) _(1,1) _(2i) _(1,2) _(,15) ⁽¹⁾ 16-23 Indices 16-23are constructed by replacing the 3rd subscript in indices 0-7 withindices 16-23 24-31 Indices 24-31 are constructed by replacing the 3rdsubscript in indices 0-7 with indices 24-31 . . . 248-255 Indices248-255 are constructed by replacing the 3rd subscript in indices 0-7with indices 255${{where}\mspace{14mu} y_{{2i_{1,1}},{2i_{1,2}},n}^{(1)}} = \begin{bmatrix}x_{{2i_{1,1}},{2i_{1,2}}} \\{x_{{2i_{1,1}},{2i_{1,2}}}\varphi_{n}}\end{bmatrix}$ x_(2i) _(1,1) _(,2i) _(1,2) is as in Table 10;$\varphi_{n} = {{diag}\left( {e^{\frac{j\; 2\; \pi \; n_{0}}{4}},e^{\frac{j\; 2\; \pi \; n_{1}}{4}},e^{\frac{j\; 2\; \pi \; n_{2}}{4}},e^{\frac{j\; 2\; \pi \; n_{3}}{4}}} \right)}$${{{with}\mspace{14mu} n_{b}} = {{\left\lfloor {\frac{n}{4^{4 - b - 1}}\mspace{14mu} {mod}\mspace{14mu} 4} \right\rfloor \mspace{14mu} {for}\mspace{14mu} b} = 0}},1,2,{3\mspace{14mu} {as}\mspace{14mu} {in}\mspace{14mu} {Table}\mspace{14mu} 15}$

TABLE 18 W3 or W22 Codebook for 1-layer CSI reporting using antennaports 15 to 14 + P i₃ or i_(2,2) 0 1 2 3 W_(2i,) _(1,1) _(2i) _(1,2)_(,i) _(2,1) _(,0) ⁽¹⁾ W_(2i,) _(1,1) _(2i) _(1,2) _(,i) _(2,1) _(,1)⁽¹⁾ W_(2i,) _(1,1) _(2i) _(1,2) _(,i) _(2,1) _(,2) ⁽¹⁾ W_(2i,) _(1,1)_(2i) _(1,2) _(,i) _(2,1) _(,3) ⁽¹⁾ 4 5 6 7 W_(2i,) _(1,1) _(2i) _(1,2)_(,i) _(2,1) _(,4) ⁽¹⁾ W_(2i,) _(1,1) _(2i) _(1,2) _(,i) _(2,1) _(,5)⁽¹⁾ W_(2i,) _(1,1) _(2i) _(1,2) _(,i) _(2,1) _(,6) ⁽¹⁾ W_(2i,) _(1,1)_(2i) _(1,2) _(,i) _(2,1) _(,7) ⁽¹⁾ 8 9 10 11 W_(2i,) _(1,1) _(2i)_(1,2) _(,i) _(2,1) _(,8) ⁽¹⁾ W_(2i,) _(1,1) _(2i) _(1,2) _(,i) _(2,1)_(,9) ⁽¹⁾ W_(2i,) _(1,1) _(2i) _(1,2) _(,i) _(2,1) _(,10) ⁽¹⁾ W_(2i,)_(1,1) _(2i) _(1,2) _(,i) _(2,1) _(,11) ⁽¹⁾ 12 13 14 15 W_(2i,) _(1,1)_(2i) _(1,2) _(,i) _(2,1) _(,12) ⁽¹⁾ W_(2i,) _(1,1) _(2i) _(1,2) _(,i)_(2,1) _(,13) ⁽¹⁾ W_(2i,) _(1,1) _(2i) _(1,2) _(,i) _(2,1) _(,14) ⁽¹⁾W_(2i,) _(1,1) _(2i) _(1,2) _(,i) _(2,1) _(,15) ⁽¹⁾ 16-23 Indices 16-23are constructed by replacing the 3rd subscript in indices 0-7 withindices 16-23 24-31 Indices 24-31 are constructed by replacing the 3rdsubscript in indices 0-7 with indices 24-31 . . . 56-63 Indices 56-63are constructed by replacing the 3rd subscript in indices 0-7 withindices 56-63${{where}\mspace{14mu} W_{{2i_{1,1}},{2i_{1,2}},n,k}^{(1)}} = \frac{y_{{2i_{1,1}},{2i_{1,2}},n}^{(1)}c_{k}}{{y_{{2i_{1,1}},{2i_{1,2}},n}^{(1)}c_{k}}}$y_(2i,) _(1,1) _(2i) _(1,2) _(,n) ⁽¹⁾ is as in Table 17;$c_{k} = {{diag}\left( {1,e^{\frac{j\; 2\pi \; k_{1}}{4}},e^{\frac{j\; 2\; \pi \; k_{2}}{4}},e^{\frac{j\; 2\; \pi \; k_{3}}{4}}} \right)}$${{{with}\mspace{14mu} k_{b}} = {{\left\lfloor {\frac{k}{4^{4 - b - 1}}\mspace{14mu} {mod}\mspace{14mu} 4} \right\rfloor \mspace{14mu} {for}\mspace{14mu} b} = 1}},2,{3\mspace{14mu} {as}\mspace{14mu} {in}\mspace{14mu} {Table}\mspace{14mu} 16}$

In some embodiments, CSI feedback enhancement with the followingadvanced CSI feedback framework may be considered. In one example,reduced space (eigenvectors)/W1 is constructed based on one of thefollowing alternatives: (1) orthogonal basis (e.g. orthogonal DFTmatrix); and (2) non-orthogonal basis (e.g. Rel. 13 Class A W1 forrank-1 and/or 2). In another example, reduced space representation/W2 isto further combine selected beams. In yet another example, granularityof weighting (phase and/or amplitude) can be either wideband only orwideband/subband, and is constructed based on one of the followingalternatives: (1) phase and amplitude and (2) phase-only weighting.

In the aforementioned embodiments, a linear combination (LC) codebookbased CSI reporting is proposed, in which a UE is configured with a LCcodebook: W=W₁W₂, where W₁ is for WB and long-term first PMI it or PMIpair (i_(1,1), i_(1,2)) feedback, which indicates a 2N₁N₂×2L basismatrix B whose columns correspond to 2L beams from a master basis set,and W₂ is for SB and short-term second PMI i₂ feedback, which indicatesa coefficient vector for linear combination of columns of B.

An illustration of the proposed LC codebook for L=4 is shown in FIG. 14.There are two alternatives for LC codebook depending on whether co-phasefor the two polarizations is reported separately or jointly with thecoefficients. In one embodiment of Alt 0 (without co-phase), theco-phase for the two polarizations is not reported separately and ismerged with coefficient reporting. In this alternative, the number ofbeams for linear combination is 2L (where 2 is for the twopolarizations, for example, +45 and −45), and hence a coefficient vectorc of length 2L is reported for each layer. The rank-1 LC pre-coder inthis case is given by W⁽¹⁾=Bc, where B corresponds to L beams for eachof the two polarizations, b₀, b₁, . . . b_(L−1) and b₀′, b₁′, . . .b_(L−1)′, i.e. the basis matrix is given by:

$B = {\quad{\begin{bmatrix}{b_{0},b_{1},{\ldots \mspace{14mu} b_{L - 1}}} & {0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} \\{0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} & {b_{0}^{\prime},b_{1}^{\prime},{\ldots \mspace{14mu} b_{L - 1}^{\prime}}}\end{bmatrix}.}}$

In the rest of the present disclosure, it is assumed that the bases forthe two polarizations are the same, i.e., b₀, b₁, . . . b_(L−1)=b₀′,b₁′, . . . b_(L−1)′. The embodiments of present disclosure, however, areapplicable to the case in which the bases for the two polarizations aredifferent, i.e., b₀, b₁, . . . b_(L−1)≠b₀′, b₁′, . . . b_(L−1)′.

In another embodiment of Alt 1 (with co-phase), the co-phase for the twopolarizations is reported separately. In this alternative, for eachlayer, a coefficient vector c of length L and a co-phase matrix ϕ forthe two polarizations of dimension 2L×L are reported. So, the rank-1 LCpre-coder is given by W⁽¹⁾=Bϕc, where ϕ corresponds to co-phase valuesϕ₀, ϕ₁, . . . ϕ_(L−1) for the two polarizations and L beams, i.e.

$\begin{bmatrix}{b_{0}b_{1}\mspace{11mu} \ldots \mspace{14mu} b_{L - 1}} & {0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} \\{0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} & {b_{0}b_{1}\mspace{11mu} \ldots \mspace{14mu} b_{L - 1}}\end{bmatrix}{\quad{\begin{bmatrix}e_{0} & e_{1} & \ldots & e_{L - 1} \\{\varphi_{0}e_{0}} & {\varphi_{1}e_{1}} & \ldots & {\varphi_{L - 1}e_{L - 1}}\end{bmatrix} = {\begin{bmatrix}b_{0} & b_{1} & \ldots & b_{L - 1} \\{\varphi_{0}b_{0}} & {\varphi_{1}b_{1}} & \ldots & {\varphi_{L - 1}b_{L - 1}}\end{bmatrix}.}}}$

In the aforementioned embodiments, the details about LC codebook basedon non-orthogonal W₁ basis, such LTE Rel. 13 Class A rank 1-2 W₁codebook, are proposed. In the next part of this disclosure, LC codebookdetails based on both non-orthogonal and orthogonal W₁ basis areproposed.

FIG. 20 illustrates an example non-orthogonal and orthogonal master beamgroups 1D port layouts (N₁>1, N₂=1) 2000 according to embodiments of thepresent disclosure. An embodiment of the non-orthogonal and orthogonalmaster beam groups 1D port layouts (N₁>1, N₂=1) 2000 shown in FIG. 20 isfor illustration only. One or more of the components illustrated in FIG.20 can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

FIG. 21 illustrates example non-orthogonal and orthogonal master beamgroups of 2D port layouts (N1>1, N2>1) 2100 according to embodiments ofthe present disclosure. An embodiment of the non-orthogonal andorthogonal master beam groups of 2D port layouts (N1>1, N2>1) 2100 shownin FIG. 21 is for illustration only. One or more of the componentsillustrated in FIG. 21 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, a UE is configured with an oversampled DFT codebookas the master basis set for the LC codebook via higher-layer RRCparameters: N₁ and O₁ for 1D antenna port layouts (i.e. N₁>1, N₂=1), asshown in FIG. 20, which comprises of O₁N₁ DFT beams; and N₁, N₂, O₁, andO₂ for 2D antenna port layouts (i.e. N₁>1, N₂>1), as shown in FIG. 21,which comprises of O₁N₁×O₂N₂ two-dimensional DFT beams, each of which isobtained by the Kronecker product of a DFT beam in the first dimensionand a DFT beam in the second dimension.

A 1D or 2D beam is illustrated as a square in FIG. 20 and FIG. 21. Thisis for illustration only. The beams can be of arbitrary shape inpractice. Using this oversampled DFT codebook, master beam groups areconstructed by selecting: for 1D layouts, L₁ beams from the oversampledDFT codebook such that the beams are uniformly-spaced, i.e., thedifference between the indices of two consecutive beams is constant; andfor 2D layouts, L₁×L₂ beams from the oversampled DFT codebook, where L₁and L₂ are the number of beams in first and second dimensions,respectively such that the beams are uniformly-spaced, i.e., thedifference between the indices of two consecutive beams in first (orsecond) dimension of the beam group is constant.

In particular, two types of master beam groups are constructed as shownin FIG. 20 and FIG. 21. In one example of non-orthogonal, the differencebetween two consecutive (or adjacent) beam indices in first (or second)dimension of the beam group is one. In another example of orthogonal,the difference between two consecutive (or adjacent) beam indices infirst (or second) dimension of the beam group is O₁ (or O₂).

An example of the master beam group with the leading beam at (0, 0) isalso shown in FIG. 21 and FIG. 22 as BG0. Two alternatives for (L₁, L₂)value are as follows: non-orthogonal with (L₁, L₂)=(8, 1) for 1D portlayouts, and (L₁, L₂)=(4, 2) if N₁≥N₂ and (L₁, L₂)=(2, 4) if N₁<N₂ for2D port layouts; and orthogonal with (L₁, L₂)=(N₁, 1) for 1D portlayouts, and (L₁, L₂)=(N₁, N₂) for 2D port layouts.

FIG. 22 illustrates example non-orthogonal and orthogonal master beamgroups with (L₁, L₂)=(4, 2) 2200 for N₁≥N₂ according to embodiments ofthe present disclosure. An embodiment of the example non-orthogonal andorthogonal master beam groups with (L₁, L₂)=(4, 2) 2200 for N₁≥N₂ shownin FIG. 22 is for illustration only. One or more of the componentsillustrated in FIG. 22 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure. Anillustration of master beam group for (L₁, L₂)=(4, 2) and N₁≥N₂ is shownin FIG. 22.

In the explanation below and in the rest of the present disclosure (L₁,L₂)=(4, 2) for N₁≥N₂ is considered for illustration, unless otherwisementioned. It is straightforward to extend the explanations andembodiments of the present disclosure to (L₁, L₂)=(2, 4) for N₁<N₂layouts.

Note that (L₁, L₂)=(4, 2) for non-orthogonal master beam groupcorresponds to master beam group in LTE Rel. 13 Class A rank 1-2codebook. Note also that (L₁, L₂)=(N₁, N₂) for orthogonal master beamgroup implies that the master beam group is full orthogonal DFT basis.

In one example, (L₁, L₂) value or/and master beam group type(non-orthogonal or orthogonal) are fixed in the specification, forexample (L₁, L₂) is fixed to be (8, 1) for 1D port layouts, and (4, 2)or (2, 4) for 2D port layouts, and master beam group type is fixed to benon-orthogonal master beam group.

In another example, the UE is configured with an (L₁, L₂) value and oneof the two types of master beam groups. This configuration is via higherlayer RRC signaling. For example, eNB configures one of the two masterbeam groups shown in FIG. 20 and FIG. 21 via 1-bit RRC parameterMasteBeamGroupType or OrthogonalBasisEnabled. When MasteBeamGroupType orOrthogonalBasisEnabled is turned “ON,” the UE uses orthogonal masterbeam group in the LC codebook. Otherwise the UE uses non-orthogonalmaster beam group.

In another example, the UE reports a preferred (L₁, L₂) value or/and apreferred master beam group type. This reporting is WB, and is eitherexplicit as a new WB CSI type or implicit with either RI or i₁ ori_(1,1) or i_(1,2), for example. Using the following configured ordetermined parameters: N₁, N₂, O₁, and O₂; (L₁, L₂); and Master beamgroup type with non-orthogonal or orthogonal. The dual-stage LC codebookW=W₁W₂ is constructed as follows.

The W₁ codebook is for WB CSI reporting and comprises of the followingthree components. In one example of Master beam group, the master beamgroup of size (L₁, L₂) and non-orthogonal or orthogonal type is selectedfrom the oversampled DFT codebook. In another example of WB beamselection, L out of L₁ beams for 1D layouts and L out of L₁×L₂ beams for2D layouts are selected from the master beam group. In yet anotherexample of WB beam power selection, WB beam power levels for L selectedbeams are selected from a codebook.

The first WB component (i.e. master beam group) is always reported usingthe first PMI i₁ or (i_(1,1), i_(1,2)).

The second WB component (i.e. L beams) is always reported and L beamsare selected from the reported master beam group. A few examples of Lvalues include 2, 4, and 8. The L value can either be fixed (e.g. L=4)or the second WB component is reported in the CSI report or the secondWB component is configured via higher layer RRC signaling. In case L isreported in the CSI report, the second WB is reported either explicitlyas a new CSI reporting type or implicitly with RI or i₁ or i_(1,1) ori_(1,2).

In the rest of the present disclosure, L is assumed to be either fixedor RRC configured to L=4.

FIG. 23 illustrates an example beam selection from a non-orthogonalmaster beam group with (L1, L2)=(8, 1) 2300 for 1D layouts according toembodiments of the present disclosure. An embodiment of the beamselection from a non-orthogonal master beam group with (L1, L2)=(8, 1)2300 shown in FIG. 23 is for illustration only. One or more of thecomponents illustrated in FIG. 23 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

FIG. 24 illustrates an example beam selection from a non-orthogonalmaster beam group with (L1, L2)=(4, 2) 2400 for 2D layouts according toembodiments of the present disclosure. An embodiment of the beamselection from a non-orthogonal master beam group with (L1, L2)=(4, 2)2400 shown in FIG. 24 is for illustration only. One or more of thecomponents illustrated in FIG. 24 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

FIG. 25 illustrates an example beam selection from an orthogonal masterbeam group with (L1, L2)=(8, 1) 2500 for 1D layouts according toembodiments of the present disclosure. An embodiment of the beamselection from an orthogonal master beam group with (L1, L2)=(8, 1) 2500shown in FIG. 25 is for illustration only. One or more of the componentsillustrated in FIG. 25 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

FIG. 26 illustrates an example beam selection from an orthogonal masterbeam group with (L₁, L₂)=(4, 2) 2600 for 2D layouts according toembodiments of the present disclosure. An embodiment of the beamselection from an orthogonal master beam group with (L₁, L₂)=(4, 2) 2600for 2D layouts shown in FIG. 26 is for illustration only. One or more ofthe components illustrated in FIG. 26 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments of L beam selection (e.g., Parameterized beamselection), the selection of L beams is based on Codebook-Configparameter. Examples of a few beam selections are shown in FIG. 23 andFIG. 24 for non-orthogonal master beam group type, and in FIG. 25 andFIG. 26 for orthogonal master beam group type assuming L=4, and (L₁,L₂)=(8, 1) for 1D layouts and (4, 2) for 2D layouts.

The selected beams are shown in black color squares. Note that beamgroups for Codebook-Config 2, 3, and 4 in FIG. 24 correspond to LTE Rel.13 Class A rank 1-2 W₁ codebook, and beam groups for Codebook-Config 2,3, and 4 in FIG. 26 correspond to LTE Rel. 13 Class A rank 7-8 W₁codebook. Similarly, beam group for Codebook-Config 4 in FIG. 23corresponds to LTE Rel. 13 Class A rank 1-2 W₁ codebook, and beam groupfor Codebook-Config 4 in FIG. 25 corresponds to LTE Rel. 13 Class A rank7-8 W₁ codebook.

There are the following alternatives for 1D port layouts. In onealternative, only Codebook-Config=4 is supported for LC codebook if theUE is configured with a 1D port layout. In another alternative, for LCcodebook, the supported Codebook-Config values for 1D port layouts are 1and 4 (same values as in LTE Rel. 13 Class A codebook for 1D layouts)with one of the following options for beam grouping: Codebook-Config 1and 4 corresponds to the same beam group (similar to LTE Rel. 13 Class Acodebook for rank 7-8), for example, the beam group for Codebook-Config4 in FIG. 23 (non-orthogonal) and FIG. 25 (orthogonal); andCodebook-Config 1 and 4 corresponds to the two different beam groups,for example, the beam groups for Codebook-Config 1 and 4 in FIG. 25(non-orthogonal) and FIG. 25 (orthogonal). In yet another alternative,for LC codebook, the supported Codebook-Config values for 1D portlayouts are 1, 2, 3, and 4, for example, the beam groups forCodebook-Config 1, 2, 3, and 4 in FIG. 23 (non-orthogonal) and FIG. 25(orthogonal). This last alternative is assumed in the rest of thepresent disclosure.

Similarly, there are the following alternatives for 2D port layouts. Inone alternative, only Codebook-Config=2, 3, and 4 are supported for LCcodebook if the UE is configured with a 2D port layout. In anotheralternative, for LC codebook, the supported Codebook-Config values for 2port layouts are 1, 2, 3, and 4 (same values as in LTE Rel. 13 Class Acodebook for 1D layouts) with one of the following options for beamgrouping: Codebook-Config 1 and 2 corresponds to the same beam group(similar to LTE Rel. 13 Class A codebook for rank 7-8), for example, thebeam group for Codebook-Config 2 in FIG. 24 (non-orthogonal) and FIG. 26(orthogonal) and Codebook-Config 1 and 2 corresponds to the twodifferent beam groups, for example, the beam groups for Codebook-Config1 and 2 in FIG. 24 (non-orthogonal) and FIG. 26 (orthogonal). Thisalternative is assumed in the rest of the present disclosure.

There are the following methods to configure or report Codebook-Config.In one embodiment, the Codebook-Config value is always fixed in thespecification. Hence, no configuration or reporting is needed. Forexample, Codebook-Config can be fixed to Codebook-Config=4 for 1D portlayouts and Codebook-Config=2 or 3 for 2D port layouts. In anotherembodiment, the UE reports a preferred Codebook-Config value in the CSIreport where this reporting is WB. For example, a 2-bit WB indication ofa preferred Codebook-Config value (one of FIG. 23-FIG. 26) is reportedin the CSI. This reporting can be explicit as a new CSI reporting typeor implicit together with RI or i₁ or i_(1,1) or i_(1,2). In anotherembodiment, Codebook-Config is configured via RRC signaling, similar toconfiguration of LTE Rel. 13 Class A codebook.

In some embodiments of unconstrained beam selection: The selected Lbeams is unconstrained and any L out of L₁L₂ beams can be reported. Inthis case, the reporting can be based on a bitmap of length L₁L₂. Forexample, a length-8 bitmap can be reported to indicate selection of Lbeams out of (L₁, L₂)=(8, 1) or (4, 2) master beam group. This reportingcan be explicit as a new CSI reporting type or implicit together with RIor i₁ or i_(1,1) or i_(1,2).

The third WB component (i.e. beam power) is reported according to one ofthe following alternatives. In one alternative, WB beam power levels arenot reported. In this case, equal beam power levels (i.e.constant-modulus LC coefficients) are assumed while deriving the LCpre-coder. In another alternative, WB beam power levels are alwaysreported using a beam power codebook. In yet another alternative, beampower reporting is configurable using a RRC parameter BeamPowerEnabled.If BeamPowerEnabled is turned ON, then WB beam power levels arereported. If BeamPowerEnabled is turned OFF, then WB beam power levelsare not reported and equal beam power levels (i.e. constant-modulus LCcoefficients) are assumed while deriving the LC pre-coder. In oneexample, BeamPowerEnabled is turned ON for Class A eMIMO-Type, andBeamPowerEnabled is turned OFF for Class B eMIMO-Type. In the lattercase, the W₂ component of the proposed LC codebook is used as the LCcodebook for Class B eMIMO-Type.

Two examples of beam power codebook are as follows. In one example ofScalar beam power codebook: power level for each beam is selected usinga N_(p)-bit uniform scalar codebook in (0, 1). For example, for N_(p)=2,the scalar codebook is {⅛, ⅜, ⅝, ⅞}. In another example of Vector beampower codebook, power level for all L beams are selected using aunit-norm vector codebook. An example of such a codebook is shown inTable 19.

TABLE 19 Vector beam power codebook Number of Total number selectedbeams of beam (L value) Power levels Beam power vectors power vectors 11 1 1 2 [7 1]  [7/8 1/8], [1/8, 7/8] 7 [6 2] [6/8 2/8], [2/8 6/8] [5 3][3/8 5/8], [5/8 3/8] [4 4] [4/8 4/8] 3 [6 1 1] [6/8, 1/8, 1/8], [1/8,6/8, 1/8], [1/8, 1/8, 6/8] 21 [5 2 1] [5/8, 2/8, 1/8], [5/8, 1/8, 2/8],[2/8, 5/8, 1/8], [2/8, 1/8, 5/8], [1/8, 5/8, 2/8], [1/8, 2/8, 5/8], [4 22] [4/8, 2/8, 2/8], [2/8, 4/8, 2/8], [2/8, 2/8, 4/8] [4 3 1] [4/8, 3/8,1/8], [4/8, 1/8, 3/8], [3/8, 4/8, 1/8], [1/8, 4/8, 3/8], [1/8, 4/8,3/8], [1/8, 3/8, 4/8] [3 3 2] [3/8, 3/8, 2/8], [3/8, 2/8, 3/8], [2/8,3/8, 3/8] 4 [5 1 1 1] [5/8, 1/8, 1/8, 1/8], [1/8, 5/8, 1/8, 1/8], [1/8,1/8, 5/8, 1/8], 35 [1/8, 1/8, 1/8, 5/8] [4 2 1 1] [4/8, 2/8, 1/8, 1/8],[4/8, 1/8, 2/8, 1/8], [4/8, 1/8, 1/8, 2/8] [2/8, 4/8, 1/8, 1/8], [1/8,4/8, 2/8, 1/8], [1/8, 4/8, 1/8, 2/8] [1/8, 2/8, 4/8, 1/8], [2/8, 1/8,4/8, 1/8], [1/8, 1/8, 4/8, 2/8] [1/8, 2/8, 1/8, 4/8], [1/8, 1/8, 2/8,4/8], [2/8, 1/8, 1/8, 4/8] [3 3 1 1] [3/8, 3/8, 1/8, 1/8], [3/8, 1/8,3/8, 1/8], [3/8, 1/8, 1/8, 3/8] [1/8, 3/8, 3/8, 1/8], [1/8, 1/8, 3/8,3/8], [1/8, 3/8, 1/8, 3/8] [3 2 2 1] [3/8, 2/8, 2/8, 1/8], [3/8, 2/8,1/8, 2/8], [3/8, 1/8, 2/8, 2/8] [2/8, 3/8, 2/8, 1/8], [2/8, 3/8, 1/8,2/8], [2/8, 2/8, 3/8, 1/8], [2/8, 2/8, 1/8, 3/8] [2/8, 1/8, 2/8, 3/8],[2/8, 1/8, 3/8, 2/8] [1/8, 3/8, 2/8, 2/8], [1/8, 2/8, 3/8, 2/8], [1/8,2/8, 2/8, 3/8] [2 2 2 2] [2/8, 2/8, 2/8, 2/8]

The breakdown of the number of WB bits for the three components is asfollows. In one example for master beam group, the range of values ofi_(1,i) and i_(1,2) is given by i_(1,1)=0, 1, 2, . . . O₁N₁/s₁ andi_(1,2)=0, 1, 2, . . . O₂N₂/s₂, where (s₁,s₂) are spacing between twoadjacent master beam groups in two dimensions. The example values of s₁(or s₂) are 1, 2, O₁/4 (or O₂/4), O₁/2 (or O₂/2), and O₁ (or O₂). So,the number of bits to report i_(1,i) and i_(1,2) is

${\log_{2}\left\lceil \frac{O_{1}N_{1}}{s_{1}} \right\rceil \mspace{14mu} {and}\mspace{14mu} \log_{2}\left\lceil \frac{O_{2}N_{2}}{s_{2}} \right\rceil},$

respectively. In another example for WB beam selection, N_(b) bits arereported, where N_(b)=2 (parameterized) or L₁L₂(unconstrained). In yetanother example for WB beam power, N_(p)=(L−1)P bits are reported, where1^(st) beam is assumed to be unit-power, and power levels for (L−1)beams are selected from a codebook assuming P bit for each beam.

So the total number of WB CSI bits is

${\log_{2}\left\lceil \frac{O_{1}N_{1}}{s_{1}} \right\rceil} + {\log_{2}\left\lceil \frac{O_{2}N_{2}}{s_{2}} \right\rceil} + N_{b} + {N_{p}.}$

If these WB bits are reported jointly, then these WB bits can bereported in i_(1,1). Alternatively, if these WB bits are reportedseparately, then the master beam group can be reported using i_(1,1) andi_(1,2), and beam selection and beam power selection can be reportedeither jointly using BGI (Beam Group Index) of N_(b)+N_(p) bits; orseparately using BGI of N_(b) bits and BPI (Beam Power Index) of N_(p)bits, respectively. In this later alternative, a new CSI reporting typefor BSI and BPI are defined in the specification.

The W₂ codebook is for per SB CSI reporting and comprises of thefollowing three components. In one embodiment, the W₂ codebook comprisesSB beam selection. In this example, the first component is B out of Lbeam selection, where 1≤B≤L and this selection is per SB. The LCcoefficient vector with beam selection matrix E_(B) can be expressed asc=E_(B)c_(B), where the length-B coefficient vector after beam selectionis c_(B)=[c₀ c₁ . . . c_(B−1)] and, for example, for 4 beams, i.e., L=4,2L×B beam selection matrix E_(B) is as given in Table 20.

TABLE 20 Beam selection matrix Number of candidate beam B${selection}\mspace{14mu} {matrices}\mspace{14mu} \begin{pmatrix}4 \\B\end{pmatrix}$ Beam selection matrix E_(B) 1 4 E_(1,0) = e₀, E_(1,1) =e₁, E_(1,2) = e₂, E_(1,3) = e₃ 2 6 E_(2,0) = [e₀ e₁], E_(2,1) = [e₀ e₂],E_(2,2) = [e₀ e₃], E_(2,3) = [e₁ e₂], E_(2,4) = [e₁ e₃], E_(2,5) = [e₂e₃] 3 4 E_(3,0) = [e₀ e₁ e₂], E_(3,1) = [e₀ e₁ e₃] E_(3,2) = [e₀ e₂ e₃],E_(3,3) = [e₁ e₂ e₃] 4 1 E_(4,0) = [e₀ e₁ e₂ e₃]

In another embodiment, the W₂ codebook comprises co-phase. In thisexample, if the configured LC codebook is according to Alt 1 in FIG. 14,then the co-phase values (for two polarizations) for B selected beamsare selected using a co-phase codebook, where co-phase values ϕ₀, ϕ₁, .. . ϕ_(B−1) for the two polarizations are selected according to one ofthe following types. In one example of single type, each co-phase valueϕ₁ is selected from a single codebook. An example of the codebook isK-PSK codebook, where a few example values of K is 2 (BPSK), 4 (QPSK),and 8 (8-PSK). In another example of double type, each co-phase value isdecomposed as ϕ_(l)=ϕ_(l) ⁽¹⁾ϕ_(l) ⁽²⁾ and is selected from a doublecodebook, C_(coph)=C_(coph) ⁽¹⁾C_(coph) ⁽²⁾, where C_(coph) ⁽¹⁾ andC_(coph) ⁽²⁾ respectively are codebooks for WB and SB components of theco-phase ϕ_(l) ⁽¹⁾ and ϕ_(l) ⁽²⁾, respectively. An example of the doublecodebook is

$C_{coph}^{(1)} = {{\left\{ {e^{j\frac{\pi}{4}},e^{j\frac{3\; \pi}{4}},e^{j\frac{5\; \pi}{4}},e^{j\frac{7\; \pi}{4}}} \right\} \mspace{14mu} {and}\mspace{14mu} C_{coph}^{(2)}} = {\left\{ {e^{j\frac{\pi}{4}},e^{{- j}\frac{\pi}{4}}} \right\}.}}$

In one example of co-phase codebook, ϕ_(l) ⁽¹⁾=ϕ_(k) ⁽¹⁾ and ϕ_(l)⁽²⁾≠ϕ_(k) ⁽²⁾ (i.e. common WB and different SB co-phase components forall beams) for all 1, k in {0, 1, . . . , B−1}.

In yet another embodiment, the W₂ codebook comprises coefficients. Inthis example, coefficients to linearly combine B selected beams areselected using a coefficient codebook, which is constant-modulus (i.e.phase only). There are two alternatives for coefficient phases. In onealternative of Vector phase codebook, the phases of coefficients arequantized jointly using a vector codebook. An example of the vectorphase codebook is an oversampled DFT codebook. Two alternatives in thiscase are as follows. In one example of single type, the coefficientphase vector c=[α₀ α₁ . . . α_(2B−1)] (Alt 0) or [α₀ α₁ . . . α_(B−1)](Alt 1) is selected from a single vector phase codebook, an example ofwhich is a DFT codebook with appropriate oversampling factor O, in whichc belongs to

$\begin{matrix}{C_{{Coef},0} = \left\{ \left\lbrack \begin{matrix}1 & e^{j\frac{2\; \pi \; k}{2{OB}}} & \ldots & {\left. {{{\left. e^{j\frac{2\; \pi \; {k{({{2B} - 1})}}}{2\; {OB}}} \right\rbrack^{T}\text{:}\mspace{11mu} k} = 0},1,\ldots \mspace{14mu},{{2{OB}} - 1}} \right\};}\end{matrix} \right. \right.} & \left( {{Alt}\mspace{14mu} 0} \right) \\{or} & \; \\{C_{{Coef},1} = \left\{ \left\lbrack \begin{matrix}1 & e^{j\frac{2\; \pi \; k}{OB}} & \ldots & {\left. {{{\left. e^{j\frac{2\; \pi \; {k{({B - 1})}}}{\; {OB}}} \right\rbrack^{T}\text{:}\mspace{11mu} k} = 0},1,\ldots \mspace{14mu},{{OB} - 1}} \right\}.}\end{matrix} \right. \right.} & \left( {{Alt}\mspace{14mu} 1} \right)\end{matrix}$

In another example of double type, the coefficient phase vector isdecomposed as c=c⁽¹⁾c⁽²⁾ and is selected from a double vector phasecodebook, an example of which is double DFT codebook in which c⁽¹⁾ andc⁽²⁾ are selected from a DFT codebook with appropriate oversamplingfactor O such that c⁽¹⁾ represents a group of K DFT vectors, and c⁽²⁾selects one DFT vector from the group. A few examples of K value are 4,8, and 16. This is similar to the Rel. 10 8-Tx dual-stage codebook.

In another alternative of scalar phase codebook, the phases ofcoefficients are quantized separately using a scalar codebook. Anexample of the scalar phase codebook is K-PSK codebook, where a fewexample values of K is 2 (BPSK), 4 (QPSK), and 8 (8-PSK). Twoalternatives in this case are as follows. In one example of single type,each coefficient phase α_(l) is selected from a single codebook, e.g.C_(coef)={1, −1, j, −j}. In another example of double type, eachcoefficient phase is decomposed as α_(l)=α_(l) ⁽¹⁾α_(l) ⁽²⁾ and isselected from a double codebook, e.g. C_(coef)=C_(coef) ⁽¹⁾C_(coef) ⁽²⁾,where C_(coef) ⁽¹⁾ and C_(coef) ⁽²⁾ respectively are codebooks for WBand SB components of the phase. An example of the double phase codebookis

$C_{coef}^{(1)} = {{\left\{ {e^{j\frac{\pi}{4}},e^{j\frac{3\; \pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{7\; \pi}{4}}} \right\} \mspace{14mu} {and}\mspace{14mu} C_{coef}^{(2)}} = {\left\{ {e^{j\frac{\pi}{4}},e^{{- j}\frac{\pi}{4}}} \right\}.}}$

In some embodiments, a new CSI parameter Beam Group Index (BGI) or BasisIndex (BI) is defined for LC codebook to indicate L beams in the W₁codebook. An example of BGI or BI to beam group mapping is shown in FIG.30 with the following two options. In one example of Option 0, BGI orBI=0-3 are mapped to Codebook-Config 1-4 in FIG. 24, and BGI or BI=4-7are mapped to Codebook-Config 1-4 in FIG. 26. In another example ofOption 1, BI=0-3 are mapped to Codebook-Config 1-4 in FIG. 24, and BGIor BI=4-7 are mapped to Codebook-Config 1-4 in FIG. 23 with inter-beamspacing (O₁,O₂) instead of (1,1) in FIG. 26. The UE is either configuredwith one of BGI or BI value for the LC codebook or reports a preferredBGI or BI in the CSI report, where this reporting is 3-bit WB (jointwith i_(1,1) or as a separate CSI component).

In some embodiments, a UE is configured with the LC codebook for rank≤r,and Class A or legacy codebooks for rank>r, where r=1, 2, 4, or 8, forexample. In one example, the LC codebook is supported for up to a fixedrank, for example r=2. In one example, the rank of the LC codebook forCSI reporting is configured. For example r=2 is configured. In thiscase, the UE uses LC codebook for rank≤r and uses legacy or Class Acodebooks for rank>r for CSI reporting.

In sub-embodiment 0, the UE is configured with the LC codebook for rank1 only, and legacy (up to LTE Rel. 13) codebook for higher ranks, forexample, rank 2-8. There are two alternatives for the configured rank 1LC codebook. In one example of Alt 0-0, the rank 1 LC codebook hasnon-orthogonal W₁ basis. For example, LTE Rel. 13 Class A rank 1-2 forCodebook-Config 2, 3, and 4. In another example of Alt 0-1, the rank 1LC codebook has orthogonal W₁ basis. For example, LTE Rel. 13 Class Arank 7-8 Codebook-Config 2, 3, and 4.

In sub-embodiment 1, the UE is configured with the LC codebook for rank1-2 only, and legacy (up to LTE Rel. 13) codebook for higher ranks, forexample, rank 3-8. There are three alternatives for the configured rank1-2 LC codebook. In one example of Alt 1-0, the rank 1-2 LC codebook hasnon-orthogonal W₁ basis. For example, LTE Rel. 13 Class A rank 1-2 forCodebook-Config 2, 3, and 4. In another example of Alt 1-1, the rank 1-2LC codebook has orthogonal W₁ basis. For example, LTE Rel. 13 Class Arank 7-8 Codebook-Config 2, 3, and 4. In yet another example of Alt 1-2,the rank 1 LC codebook has non-orthogonal W₁ basis. For example, LTERel. 13 Class A rank 1-2 for Codebook-Config 2, 3, and 4. The rank 2 LCcodebook has orthogonal W₁ basis. For example, LTE Rel. 13 Class A rank7-8 Codebook-Config 2, 3, and 4.

In sub-embodiment 2, the UE is configured with the LC codebook for rank1-4 only, and legacy (up to LTE Rel. 13) codebook for higher ranks, forexample, rank 5-8. There are four alternatives for the configured rank1-4 LC codebook. In one example of Alt 2-0, the rank 1-4 LC codebook hasnon-orthogonal W₁ basis. For example, LTE Rel. 13 Class A rank 1-4 forCodebook-Config 2, 3, and 4. In another example of Alt 2-1, the rank 1-4LC codebook has orthogonal W₁ basis. For example, LTE Rel. 13 Class Arank 7-8 Codebook-Config 2, 3, and 4. In yet another example of Alt 2-2,the rank 1 LC codebook has non-orthogonal W₁ basis. For example, LTERel. 13 Class A rank 1-2 for Codebook-Config 2, 3, and 4. The rank 2-4LC codebook has orthogonal W₁ basis. For example, LTE Rel. 13 Class Arank 7-8 Codebook-Config 2, 3, and 4. In yet another example of Alt 2-3,the rank 1-2 LC codebook has non-orthogonal W₁ basis. For example, LTERel. 13 Class A rank 1-2 for Codebook-Config 2, 3, and 4. the rank 3-4LC codebook has orthogonal W₁ basis. For example, LTE Rel. 13 Class Arank 7-8 Codebook-Config 2, 3, and 4.

In sub-embodiment 3, the UE is configured with the LC codebook for allrank, for example, rank 1-8. There are four alternatives for theconfigured LC codebook. In one example of Alt 2-2, the rank 1 LCcodebook has non-orthogonal W₁ basis. For example, LTE Rel. 13 Class Arank 1-2 for Codebook-Config 2, 3, and 4. The rank 2-8 LC codebook hasorthogonal W₁ basis. For example, LTE Rel. 13 Class A rank 7-8Codebook-Config 2, 3, and 4. In another example of Alt 2-3, the rank 1-2LC codebook has non-orthogonal W₁ basis. For example, LTE Rel. 13 ClassA rank 1-2 for Codebook-Config 2, 3, and 4. The rank 3-8 LC codebook hasorthogonal W₁ basis. For example, LTE Rel. 13 Class A rank 7-8Codebook-Config 2, 3, and 4.

In some embodiments, a UE is configured with one of non-orthogonal ororthogonal W₁ basis for LC codebook based on the LTE Rel. 13Codebook-Config parameter. In one example, orthogonal basis isconfigured using Codebook-Config 1 and 4, and non-orthogonal basis isconfigured using Codebook-Config 2 and 3. In another example, orthogonalbasis is configured using Codebook-Config 1 and 2, and non-orthogonalbasis is configured using Codebook-Config 3 and 4.

In some embodiments, for 4/8/12/16/20/24/28/32 antenna ports as shown inFIG. 12 and FIG. 13, a UE is configured with the LC codebook dependingon the RRC parameter LCCodebookEnabled. If LCCodebookEnabled is turnedOFF, then the UE is configured with legacy (up to LTE Rel. 13 and theirextensions in LTE Rel. 14) codebooks. If LCCodebookEnabled is turned ON,then the UE is configured with the proposed LC codebook.

In some embodiments, for 4/8 antenna ports with legacy (up to Rel. 12)port layouts as shown in FIG. 12, the Class A codebook parameters (N₁,N₂), (O₁, O₂), and Codebook-Config are defined as follows: 4 ports:(N₁,N₂)=(2, 1), (O₁, O₂)=(16,-), and Codebook-Config=4; and 8 ports:(N₁, N₂)=(4, 1), (O₁, O₂)=(8,-), and Codebook-Config=4.

In some embodiments, for 4/8/12/16/20/24/20/32 antenna ports, ifLCCodebookEnabled is turned ON, then: for Codebook-Config=2, 3, 4, theproposed LC codebook is used to derive CSI report; and forCodebook-Config=1, there are two alternatives for the codebook to deriveCSI report. In one example, legacy (up to LTE Rel. 13 and theirextensions in LTE Rel. 14) codebooks. In another example, LC codebookwith a new or LTE Rel. 13 W₁, for example, W₁ beam group can be LTE Rel.13 Class A rank 7-8 W₁. If LCCodebookEnabled is turned OFF, then non-LCcodebook such as legacy (up to LTE Rel. 13 and their extensions in LTERel. 14) is used.

In some embodiments, a UE is configured with the LC codebook with L=4whose W₁ component is constructed using non-orthogonal master beam group(corresponding beam groups are shown in FIG. 23 and FIG. 24), which areconfigured using a higher-layer RRC parameter Codebook-Config. Theresultant rank 1 and rank 2 W₁ codebook in this case is shown in Table22.

TABLE 22 W₁ Codebook for 1-layer and 2-layer CSI reporting using antennaports 15 to 14 + P Value of Codebook- Config Configuration 1 N₂ = 1i_(1,1) i_(1,2) $0,1,\ldots \mspace{20mu},{\frac{N_{1}O_{1}}{2} - 1}$0 x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{{2i_{1,1}} + 1},{2i_{1,2}}} & v_{{{2i_{1,1}} + 6},{2i_{1,2}}} & v_{{{2i_{1,1}} + 7},{2i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{{2i_{1,2}} + 1}} & v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}} & v_{{{2i_{1,1}} + 2},{2i_{1,2}}} & v_{{{2i_{1,1}} + 3},{2i_{1,2}}}\end{bmatrix}}$ N₁ < N₂ i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{{2i_{1,1}} + 1},{2i_{1,2}}} & v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}} & v_{{2i_{1,1}},{{2i_{1,2}} + 2}} & v_{{2i_{1,1}},{{2i_{1,2}} + 3}}\end{bmatrix}}$ 2 N₂ = 1 i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$ 0 x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{{2i_{1,1}} + 1},{2i_{1,2}}} & v_{{{2i_{1,1}} + 4},{2i_{1,2}}} & v_{{{2i_{1,1}} + 5},{2i_{1,2}}}\end{bmatrix}}$ N₁ > 1, N₂ > 1 i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{{2i_{1,1}} + 1},{2i_{1,2}}} & v_{{2i_{1,1}},{{2i_{1,2}} + 1}} & v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}}\end{bmatrix}}$ 3 N₂ = 1 i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$ 0$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{{2i_{1,1}} + 3},{2i_{1,2}}} & v_{{{2i_{1,1}} + 5},{2i_{1,2}}} & v_{{{2i_{1,1}} + 7},{2i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{{2i_{1,1}} + 2},{2i_{1,2}}} & v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}} & v_{{{2i_{1,1}} + 3},{{2i_{1,2}} + 1}}\end{bmatrix}}$ N₁ < N₂ i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{2i_{1,1}},{{2i_{1,2}} + 2}} & v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}} & v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 3}}\end{bmatrix}}$ 4 N₂ = 1 i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$ 0 x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{{2i_{1,1}} + 1},{2i_{1,2}}} & v_{{{2i_{1,1}} + 2},{2i_{1,2}}} & v_{{{2i_{1,1}} + 3},{2i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{{2i_{1,1}} + 1},{2i_{1,2}}} & v_{{{2i_{1,1}} + 2},{2i_{1,2}}} & v_{{{2i_{1,1}} + 3},{2i_{1,2}}}\end{bmatrix}}$ N₁ < N₂ i_(1,1) i_(1,2)$0,1,\ldots \mspace{14mu},{\frac{N_{1}O_{1}}{2} - 1}$$0,1,\ldots \mspace{14mu},{\frac{N_{2}O_{2}}{2} - 1}$ x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{2i_{1,1}},{2i_{1,2}}} & v_{{2i_{1,1}},{{2i_{1,2}} + 1}} & v_{{2i_{1,1}},{{2i_{1,2}} + 2}} & v_{{2i_{1,1}},{{2i_{1,2}} + 3}}\end{bmatrix}}$

In some embodiments, a UE is configured with the LC codebook with L=4whose W₁ component is constructed using orthogonal master beam group(corresponding beam groups are shown in FIG. 25 and FIG. 26), which areconfigured using a higher-layer RRC parameter Codebook-Config. Theresultant rank 1 and rank 2 W₁ codebook in this case is shown in Table23.

TABLE 23 W₁ Codebook for 1-layer and 2-layer CSI reporting using antennaports 15 to 14 + P P = 4 Value of Codebook- Config Configuration i_(1,1)i_(1,2) 1-4 N₂ = 1 0,1, . . . ,4N₁ 0 x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ P = 8 Value of Codebook- Config Configuration 1-4 N₂ = 1i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ = N₂ i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . . ,4N₂x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}}\end{bmatrix}}$ P = 12 Value of Codebook- Config Configuration 1 N₂ = 1i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {5O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . .,4N₂ x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{2}}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}}\end{bmatrix}}$ N₁ < N₂ i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . . ,4N₂x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + {2O_{2}}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{2}},{{\frac{O_{2}}{4}i_{1,2}} + {3O_{2}}}}\end{bmatrix}}$ 2 N₂ = 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {4O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {5O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ > 1, N₂ > 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . .. ,4N₂ x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}}\end{bmatrix}}$ 3 N₂ = 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {4O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {5O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . .,4N₂ x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}}\end{bmatrix}}$ N₁ < N₂ i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . . ,4N₂x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + {2O_{2}}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}}\end{bmatrix}}$ 4 N₂ = 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . .,4N₂ x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ < N₂ i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . . ,4N₂x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + {2O_{2}}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + {3O_{2}}}}\end{bmatrix}}$ P = 16/20/24/28/32 Value of Codebook- ConfigConfiguration 1 N₂ = 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {6O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {7O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . .,4N₂ x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{2}}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}}\end{bmatrix}}$ N₁ < N2 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . . ,4N₂x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + {2O_{2}}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{2}},{{\frac{O_{2}}{4}i_{1,2}} + {3O_{2}}}}\end{bmatrix}}$ 2 N₂ = 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {4O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {5O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ > 1, N₂ > 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . .. ,4N₂ x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}}\end{bmatrix}}$ 3 N₂ = 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i) _(1,1)_(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {4O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {6O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . .,4N₂ x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{1}}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}}\end{bmatrix}}$ N₁ < N₂ i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . . ,4N₂x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + {2O_{2}}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{{\frac{O_{2}}{4}i_{1,2}} + {3O_{2}}}}\end{bmatrix}}$ 4 N₂ = 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0 x_(i1,1,i1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ ≥ N₂ > 1 i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . .,4N₂ x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + O_{1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {2O_{1}}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{{\frac{O_{1}}{4}i_{1,1}} + {3O_{1}}},{\frac{O_{2}}{4}i_{1,2}}}\end{bmatrix}}$ N₁ < N₂ i_(1,1) i_(1,2) 0,1, . . . ,4N₁ 0,1, . . . ,4N₂x_(i) _(1,1) _(,i) _(1,2)$x_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\begin{bmatrix}v_{{\frac{O_{1}}{4}i_{1,1}},{\frac{O_{2}}{4}i_{1,2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + O_{2}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + {2O_{2}}}} & v_{{\frac{O_{1}}{4}i_{1,1}},{{\frac{O_{2}}{4}i_{1,2}} + {3O_{2}}}}\end{bmatrix}}$

In some embodiments, a UE is configured with a dual-stage or double LCcodebook: W=W1W2 which supports both non-orthogonal (e.g. LTE Rel. 13 or14 Class A rank 1 W1 basis) and unrestricted or unconstrained orthogonalW1 basis (based on DFT basis). In one alternative of such a codebook,referred to as CB0, rank 1 is defined that the W1 codebook correspondsto the W1 codebook in LTE Rel. 13 (and an extension in LTE Rel. 14)Class A codebook for Codebook-Config 2, 3, and 4, and rank 2 is definedthat the W1 codebook corresponds to unrestricted orthogonal W1.

In another alternative of such a codebook, referred to as CB1,Codebook-Config 2, 3, 4 is defined that W1 codebook corresponds to theW1 codebook in LTE Rel. 13 (and an extension in LTE Rel. 14) Class Acodebook for both rank 1 and 2, and Codebook-Config 1 is defined that W1codebook corresponds to unrestricted orthogonal W1 for both rank 1 and2.

In some embodiments, a UE is configured with an LC codebook, CB1, viahigher layer RRC signaling of N₁, N₂, O₁, O₂, and Codebook-Config, whoseW1 codebook is constructed based on a basis comprising of L′ beams(shown as black squares) as shown to FIG. 31. The leading beam (0, 0) ofthe basis is indicated by (i_(1,1)′, i_(1,2)), where i_(1,1)′=0, 1, . .. , O₁N₁/s₁ and i_(1,2)=0 for 1D port layouts (N₂=1), and i_(1,2)=0, 1,. . . , O₂N₂/s₂ for 2D port layouts.

Three alternatives for (s₁, s₂) are (1, 1), (2, 2) and

$\left( {\frac{O_{1}}{4},\frac{O_{2}}{2}} \right)$

for 2D and (1, -), (2, -), and

$\left( {\frac{O_{1}}{4}, -} \right)$

for 1D port layouts. So, the number of bits to report i_(1,1)′ andi_(1,2) is

${B_{1} = {{\left\lceil {\log_{2}\frac{O_{1}N_{1}}{s_{1}}} \right\rceil \mspace{14mu} {and}\mspace{14mu} B_{2}} = \left\lceil {\log_{2}\frac{O_{2}N_{2}}{s_{2}}} \right\rceil}},$

respectively. The value of L′ depends on the Codebook-Config and antennaports layouts.

If Codebook-Config=1, then the basis for W1 codebook is as follows. Inone example of 1D port layouts with 4 ports, in this case N₁=2 and N₂=1,and the basis has L′=2 orthogonal beams as shown in FIG. 31. In oneexample of 1D port layouts with 8 ports, in this case N₁=4 and N₂=1, andthe basis has L′=4 orthogonal beams as shown in FIG. 31. In one exampleof 1D port layouts with {16, 20, 24, 28, 32} ports, in this case N₁≥8and N₂=1, and the basis has L′=8 orthogonal beams as shown in FIG. 31.

In one example of 2D port layouts with 8 ports, in this case N₁=2 andN₂=2, and the basis has L′=4 orthogonal beams as shown in FIG. 31. Inone example of 2D port layouts with 12 ports, in this case (N₁, N₂)=(3,2) or (2, 3), and the basis has L′=6 orthogonal beams as shown in FIG.31. In one example of 2D port layouts with {16, 20, 24, 28, 32} ports,in this case (N₁, N₂) is such that N₁×N₂≥8 and either N₁≥N₂ or N₁<N₂,and the basis has L′=8 orthogonal beams as shown in FIG. 31.

If Codebook-Config=2 or 3, then the basis for W1 codebook is defined as2D port layouts with {8, 16, 20, 24, 28, 32} ports. In this case (N₁,N₂) is such that either N₁≥N₂ or N₁<N₂, and the basis has L′=4non-orthogonal beams as shown in FIG. 31 (same as in LTE Rel. 13 Class AW1 codebook).

If Codebook-Config=4, then the basis for W1 codebook is as follows. Inone example of 1D port layouts with {4, 8, 16, 20, 24, 28, 32} ports, inthis case (N₁, N₂) is such that either N₁≥2 or N₂=1, and the basis hasL′=4 non-orthogonal beams as shown in FIG. 31 (same as in LTE Rel. 13Class A W1 codebook). In another example of 2D port layouts with {8, 16,20, 24, 28, 32} ports, in this case (N₁, N₂) is such that either N₁≥N₂or N₁<N₂, and the basis has L′=4 non-orthogonal beams as shown in FIG.31 (same as in LTE Rel. 13 Class A W1 codebook).

In some embodiments of beam selection, to construct LC pre-coder, L outof L′ beams in the basis are selected, where L=2, 4. The value of L iseither fixed in the specification (e.g. L=4) or the UE is configuredwith one of L=2 or 4 via 1-bit higher layer RRC parameter signaling. Inone example of Codebook-Config=1, the beam selection is WB. In anotherexample of Codebook-Config=2, 3, 4, the beam selection is either WB orper SB.

The number of bits for beam selection, B, is reported jointly with thatto report i_(1,1)′ if reported WB and with that to report i₂ if reportedper SB. In one alternative, B bits correspond to the least significantbits (LSB) of the joint report. In another alternative, B bitscorrespond to the most significant bits (MSB) of the joint report. Table25 summarizes the number of bits for beam selection.

TABLE 25 Number of bits for beam selection from the basis Number of bits(B) for L out of L′ Codebook- Port layouts, Number Number of${{beam}\mspace{14mu} {selection}},\; \left\lceil {\log_{2}\begin{pmatrix}L^{\prime} \\L\end{pmatrix}} \right\rceil$ Config of ports beams (L′) L = 2 L = 4 11D, 4 ports 2 1 — 1D, 8 ports 4 3 0 1D, {16, 20, 24, 28, 32} 8 5 7 ports2D, 8 ports 4 3 0 2D, 12 ports 6 4 4 2D, {16, 20, 24, 28, 32} 8 5 7ports 2 2D, {8, 16, 20, 24, 28, 4 3 0 32} ports 3 2D, {8, 16, 20, 24,28, 4 3 0 32} ports 4 1D, {4, 8, 16, 20, 24, 28, 4 3 0 32} ports 2D, {8,16, 20, 24, 28, 4 3 0 32} ports

If Codebook-Config=2, 3, and 4, then the UE reports the first PMI pair(i_(1,1), i_(1,2)) where i_(1,1)=i_(1,1)′ if beam selection is reportedper SB in i₂, otherwise i_(1,1)=0, 1, . . . , 2^(B+B) ¹ −1 if the beamselection is reported WB.

In some embodiments of Beam power, if Codebook-Config=1, then power (oramplitude) of L beams are also reported jointly in the first PMIi_(1,1). Without loss of generality, we can assume that the power of thestrongest of the L beams is 1. Let P be the number of bits to reportbeam powers. There are two options to report beam power. In one exampleof option 0, the leading beam (0, 0) (in FIG. 31) of the basiscorresponds to the strongest beam, which is indicated by (i_(1,1)′,i_(1,2)). So, no additional indication of the strongest beam is needed.In another example of Option 1, log₂ L bits are used to indicate thestrongest beam.

Let M bits are used to report beam power per beam. Then, P=(L−1)M forAlt 0 and P=(L−1)M+log₂ L for Alt 1. The number of bits for beam power,P, is reported jointly with that to report i_(1,1)′. The UE reports thefirst PMI pair (i_(1,1), i_(1,2)) where i_(1,1)=0, 1, . . . , 2^(P+B+B)¹ −1.

In one alternative, P bits correspond to the least significant bits(LSB) of the joint report. In another alternative, P bits correspond tothe most significant bits (MSB) of the joint report.

It is assumed that for each beam, the same beam power is applied for thepolarizations, i.e.,

$\quad{\begin{bmatrix}\begin{matrix}1 & 0 & \ldots & 0 \\0 & \sqrt{p_{1}} & \ldots & 0 \\0 & 0 & \ddots & 0 \\0 & 0 & \ldots & \sqrt{p_{L - 1}}\end{matrix} & 0 \\0 & \begin{matrix}1 & 0 & \ldots & 0 \\0 & \sqrt{p_{1}} & \ldots & 0 \\0 & 0 & \ddots & 0 \\0 & 0 & \ldots & \sqrt{p_{L - 1}}\end{matrix}\end{bmatrix}{\quad{\begin{bmatrix}\begin{matrix}b_{0} & b_{1} & \ldots & b_{L - 1}\end{matrix} & \begin{matrix}0 & 0 & \ldots & 0\end{matrix} \\\begin{matrix}0 & 0 & \ldots & 0\end{matrix} & \begin{matrix}b_{0} & b_{1} & \ldots & b_{L - 1}\end{matrix}\end{bmatrix}.}}}$

In some embodiments of Number of bits to report (i_(1,1), i_(1,2)), thenumber of bits to report the first PMI pair (i_(1,1), i_(1,2)) aresummarized in Table 26 for

${\left( {s_{1},s_{2}} \right) = \left( {\frac{O_{1}}{4},\frac{O_{2}}{4}} \right)},$

M=2, (N₁, N₂)=(4, 4) and Option 0 to report beam power. Note that forOption 1 to report beam power, log₂ L additional bits are reported. Notealso that the number of bits to report the first PMI pair can fit intothe PUCCH Format 3 based periodic CSI reporting.

TABLE 26 Number of bits for the first PMI pair (i_(1, 1), i_(1, 2))reporting Number of L = 2 beams L = 4 beams Codebook- beams (L′) TotalTotal Config in the basis (B₁, B₂) B P #bits B P #bits 1 8 (2, 4) 5 2 137 6 19 2, 3, 4 4 (4, 4) 0 0 8 0 0 14

In some embodiments, a UE is configured with an LC codebook, CB1, whichsupports fewer Codebook-Config values. For instance, the supportedCodebook-Config values are according to one of the followingcombinations. In one example of 2 Codebook-Config values, combination 0is defined as Codebook-Config=1 (unrestricted W1) and Codebook-Config=2(LTE Rel. 13 Class A rank 1 W1); combination 1 is defined asCodebook-Config=1 (unrestricted W1) and Codebook-Config=3 (LTE Rel. 13Class A rank 1 W1); and combination 2 is defined as Codebook-Config=1(unrestricted W1) and Codebook-Config=4 (LTE Rel. 13 Class A rank 1 W1).In another example of 3 Codebook-Config values, combination 3 is definedas Codebook-Config=1 (unrestricted W1) and Codebook-Config=2 and 3 (LTERel. 13 Class A rank 1 W1); combination 4 is defined asCodebook-Config=1 (unrestricted W1) and Codebook-Config=2 and 4 (LTERel. 13 Class A rank 1 W1); and combination 5 is defined asCodebook-Config=1 (unrestricted W1) and Codebook-Config=3 and 4 (LTERel. 13 Class A rank 1 W1). In yet another example of 4 Codebook-Configvalues, combination 6 is defined as Codebook-Config=1 (unrestricted W1)and Codebook-Config=2, 3, and 4 (LTE Rel. 13 Class A rank 1 W1). Onlyone of these Combination 0-6 will be supported and specified in thespecification.

In some embodiments, a UE is configured with an LC codebook, CB2, whichis the exactly the same as CB1, except that the basis forCodebook-Config=1 is the full orthogonal DFT basis comprising of N₁×N₂orthogonal beams. The basis for different antenna port layouts areillustrated in FIG. 32. Note that when compared with CB1 in previousembodiments, CB2 requires more number of bits (B) for L out of L′ beamselection.

In some embodiments, the W2 codebook in the above-mentioned LCcodebooks, CB0, CB1, and CB2 are according to one of the followingalternatives: for both rank 1 and 2, the W2 codebook (for LCcoefficients) is the same for the two types of W1, orthogonal W1 forCodebook-Config 1, and non-orthogonal W1 for Codebook-Config 2, 3, and4; for rank 1, the W2 codebook is the same for the two types of W1, andfor rank 2, it is different; for rank 2, the W2 codebook is the same forthe two types of W1, and for rank 1, it is different; and for both rank1 and 2, the W2 codebook is different for the two types of W1. In theseW2 codebook alternatives, the W2 codebook is according to someembodiment of the present disclosure.

In some embodiments, a UE is configured with a dual-stage or double LCcodebook: W=W1W2 which supports both non-orthogonal (LTE Rel. 13 or 14Class A rank 1 W1 basis) and orthogonal W1 basis (LTE Rel. 13 or 14Class A rank 3/5/7 W1 basis). In one alternative of such a codebook,referred to as CB3, rank 1 is defined that the W1 codebook correspondsto the rank 1 W1 codebook in LTE Rel. 13 (and an extension in LTE Rel.14) Class A codebook for Codebook-Config 2, 3, and 4, and rank 2 isdetermined that the W1 codebook corresponds to rank>2 W1 codebook in LTERel. 13 (and an extension in LTE Rel. 14) Class A codebook forCodebook-Config 2, 3, and 4. In one sub-alternative (CB3-0), the rank 2W1 LC codebook corresponds to LTE Rel. 13 (or 14) rank 3 Class A W1codebook. In another sub-alternative (CB3-1), the rank 2 W1 LC codebookcorresponds to LTE Rel. 13 (or 14) rank 5 Class A W1 codebook. Inanother sub-alternative (CB3-2), the rank 2 W1 LC codebook correspondsto LTE Rel. 13 (or 14) rank 7 Class A W1 codebook.

In another alternative of such a codebook, referred to as CB4,Codebook-Config 2, 3, 4 is defined that W1 codebook corresponds to theW1 codebook in LTE Rel. 13 (and an extension in LTE Rel. 14) Class Acodebook for both rank 1 and 2, and Codebook-Config 1 is defined that W1codebook corresponds to rank>2 W1 codebook in LTE Rel. 13 (and anextension in LTE Rel. 14) Class A codebook for both rank 1 and 2. In onesub-alternative (CB4-0), the rank 1 and rank 2 W1 LC codebookcorresponds to LTE Rel. 13 (or 14) rank 3 Class A W1 codebook. Inanother sub-alternative (CB4-1), the rank 1 and rank 2 W1 LC codebookcorresponds to LTE Rel. 13 (or 14) rank 5 Class A W1 codebook. Inanother sub-alternative (CB4-2), the rank 1 and rank 2 W1 LC codebookcorresponds to LTE Rel. 13 (or 14) rank 7 Class A W1 codebook.

For Codebook-Config=1, i.e., codebooks CB4-0, CB4-1, and CB4-2, thereare four possible rank 3/5/7 Class A W1 codebooks (for four LTE Rel. 13Class A Codebook-Config values). It may be proposed to select two ofthem depending on antenna port layouts if Codebook-Config=1 isconfigured for LC codebook. In one example of 1D antenna port layouts,the Class A W1 codebook in codebooks CB4-0, CB4-1, and CB4-2 correspondsto Codebook-Config=4). In another example of 2D antenna port layouts:the Class A W1 codebook in codebooks CB4-0, CB4-1, and CB4-2 correspondsto Codebook-Config=2).

FIG. 27 illustrates an example LC codebook CB4-2 2700 according toembodiments of the present disclosure. An embodiment of the LC codebookCB4-2 2700 shown in FIG. 27 is for illustration only. One or more of thecomponents illustrated in FIG. 27 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

An illustration of this proposal for CB4-2 is shown in FIG. 27. Asshown, if Codebook-Config 1 is configured for LC codebook CB4-2, thenfor 1D port layouts, 4 orthogonal beams (shown as black squares) form aline and correspond to Codebook-Config 4 in LTE Rel. 13 rank 7 Class Acodebook, and for 2D port layouts, 4 orthogonal beams (shown as blacksquares) form a square and correspond to Codebook-Config 2 in LTE Rel.13 rank 7 Class A codebook.

The W₁ and W₂ codebook details for LC codebook CB4-2 are as follows. Inone embodiment of Codebook-Config=1, W₁ codebook comprises of thefollowing components: fixed orthogonal basis as in LTE Rel. 13 Class Arank 7 W₁ codebook for Codebook-Config=2 (2D port layouts) and 4 (IDport layouts); L={2, 4} beams which are selected WB from the selectedorthogonal basis; and strongest beam index. In such instance, there aretwo alternatives for the strongest beam indication; the beam at (0, 0)is the strongest beam, so no indication is needed; and the index of thestrongest beam in the reported orthogonal basis is indicated, whichrequires log₂ 4=2 bits indication. If L=2, then index of remaining 1 outof 3 beam, which requires log₂(₁ ³)=2 bits. In such instance of beampower levels for L−1 beams, assuming 2 bits per beam, the index of thebeam requires 2(L−1) bits. Note that the strongest beam power is 1. Anexample of 2-bit beam power codebook is {1, √{square root over (0.5)},√{square root over (0.25)}, √{square root over (0.125)}}. Anotherexample of 2-bit beam power codebook is {1, √{square root over (0.5)},√{square root over (0.25)}, 0}.

W₂ codebook comprises of LC coefficient vectors c^((r))=[1 c₁ ^((r)) . .. c_(L−1) ^((r)) ϕ₀ ^((r)) ϕ₁ ^((r))c₁ ^((r)) . . . ϕ_(L−1)^((r))c_(L−1) ^((r))]^(T) where r=0, R−1 are for R layers, [ϕ₀ ^((r)) ϕ₁^((r)) . . . ϕ_(L−1) ^((r))]^(T) are L co-phase values for layer r, [1c₁ ^((r)) . . . c_(L−1) ^((r))]^(T) are L coefficients for layer r, andboth ϕ_(l) ^((r)) and c_(l) ^((r)) belong to QPSK alphabet for each rand l. The detailed proposal about W₂ codebook is provided later in thepresent disclosure.

In another embodiment of Codebook-Config=2, 3, 4, W₁ codebook comprisesof non-orthogonal basis as in LTE Rel. 13 Class A rank 1 W₁ codebook forCodebook-Config=2, 3, 4; and W₂ codebook comprises of the followingcomponents: L={2, 4} beams which are selected SB (if L=2); and LCcoefficient vectors c^((r)) are as explained for Codebook-Config=1.

The W₁ beam group can then be expressed as

${W_{1} = \begin{bmatrix}{B \cdot P} & 0 \\0 & {B \cdot P}\end{bmatrix}},$

where B=[b_(k) _(1,0) _(,k) _(2,0) b_(k) _(1,1) _(,k) _(2,1) . . . b_(k)_(1,L−1) _(,k) _(2,L−1) ] whose columns correspond to L W₁ beams; and

$P = \begin{bmatrix}1 & 0 & 0 & 0 \\0 & p_{1} & 0 & 0 \\0 & 0 & \ddots & 0 \\0 & 0 & 0 & p_{L - 1}\end{bmatrix}$

if Codebook-Config=1, then p_(i) corresponds to the squared-root of beampower; otherwise P is an identity matrix.

The spacing between leading beams of two adjacent beam groups, denotedas (s₁, s₂), determines the number of bits needed to indicate a beamgroup using the first PMI pair

${{\left( {i_{1,1},i_{1,2}} \right)\text{:}\mspace{11mu} i_{1,1}} = 0},1,{{\ldots \; \frac{N_{1}O_{1}}{s_{1}}} - {1\mspace{14mu} {and}}}$${i_{1,2} = 0},1,{{\ldots \mspace{11mu} \frac{N_{2}O_{2}}{s_{2}}} - 1}$

indicate a W₁ beam group.

Since the oversampling factor (O₁, O₂) can take a value from {(4, 4),(8, 4), (8, 8), (4, -), (8, -)} depending on the antenna port layouts,for simplicity, we propose to set (s₁, s₂)=(O₁/4, O₂/4) for 2D portlayouts and (O₁/4, -) for 1D port layouts, regardless of the number ofantenna ports and Codebook-Config parameter value. Note that this choiceof (s₁, s₂) parameter ensures that the effective oversampling across theleading beams of the beam groups is 4. Also, the overhead associatedwith the beam group selection does not change across antenna portlayouts. For Codebook-Config 1-4, all WB W₁ codebook components arereported jointly as the first PMI pair (i_(1,1), i_(1,2)) and all SB W₂codebook components are reported jointly as the second PMI i₂.

If c_(l) ^((r)) and ϕ_(l) ^((r)) belong to QPSK alphabet {1, −1, j, −j},then the number of bits to report rank-2 LC coefficients (i.e. 2^(nd)PMI reporting overhead associated with W₂ codebook) is log₂4^(2(2L−1))=4(2L−1). This implies that the 2^(nd) PMI reporting overheadis doubled when compared with that for rank-1. This increase in PMIreporting overhead is an issue if 2^(nd) PMI has to be reportedperiodically using PUCCH because the limited number of CSI bits that canbe reported using PUCCH. For example, if L=4, then the number of bits toreport rank 1 and rank 2 2^(nd) PMIs are respectively 14 and 28 bits.While 14 bits rank 1 2^(nd) PMI can be reported, for example, usingPUCCH Format 3, 28 bits rank 2 2^(nd) PMI can't. It is therefore desiredto design higher rank LC codebooks (e.g. rank 2) with PMI reportingoverhead comparable to that for rank 1 and keeping periodic CSIreporting on PUCCH in mind. To reduce 2^(nd) PMI reporting overhead forrank 2 LC codebook, we can exploit the structure in the coefficientvector (because of decoupling of co-phase and coefficients): c^((r))=[1c₁ ^((r)) . . . c_(L−1) ^((r)) ϕ₀ ^((r)) ϕ₁ ^((r))c₁ ^((r)) . . .ϕ_(L−1) ^((r))c_(L−1) ^((r))]^(T).

Two alternatives (CB0 and CB1) for rank 2 LC W₂ codebook are proposed inTable 28. For comparison, the alternative (CB2) in which co-phase andcoefficients of two layers are treated independently is also shown inthe table. Note that the number of bits for rank 1 LC codebook assumingQPSK alphabet for co-phase and coefficients are 6+3 and 14 for L=2 and4, respectively. We can observe that the proposed CB0 and CB1 maintainedthe W₂ reporting payload to be the same as rank 1. The payload doublesfor CB2.

TABLE 28 Rank 2 LC codebook alternatives and W2 reporting payload CB0CB1 CB2 Co-phase [ϕ_(l) ⁽⁰⁾ ϕ_(l) ⁽¹⁾] ϵ {[1 −1], [j −j], [−1 1], [−jj]} ϕ_(l) ⁽⁰⁾, ϕ_(l) ⁽¹⁾ ϵ [ϕ_(l) ⁽⁰⁾ ϕ_(l) ⁽¹⁾] {1, j, −1, −j} (2^(nd)antenna polarization) Coefficient c_(l) ⁽⁰⁾ = c_(l) ⁽¹⁾ ϵ [c_(l) ⁽⁰⁾c_(l) ⁽¹⁾] ϵ c_(l) ⁽⁰⁾, c_(l) ⁽¹⁾ ϵ [c_(l) ⁽⁰⁾ c_(l) ⁽¹⁾] {1, j, −1, −j}{[1 −1], [j −j], [−1 1], [−j j]} {1, j, −1, −j} Co-phase 2L — (bits)Coefficient 2(L − 1) 2(L − 1) 8L − 4 (bits) Total (bits) 4L − 2 4L − 28L − 4 L = 2 (bits)  6 + 3  6 + 3 12 + 3 L = 4 (bits) 14 14 28

The W₁ and W₂ reporting payloads for the proposed rank 2 LC codebook(CB0 and CB1) is shown in Table 29, where we assume that N₁=N₂=O₁=O₂=4.In this table, the overhead of L=2 out of 4 beams (6 such selectionpossibilities) is taken into consideration.

TABLE 29 W1 and W2 reporting payload Config 1 Config 2, 3, 4 L W₁ (bits)W₂ (bits) L W₁ (bits) W₂ (bits) 2 12 6 2 8 9 4 8 10 4 8 14

In the following embodiments and elsewhere in disclosure, the co-phaserefers to the weighting applied to one (e.g. −45) of the two antennapolarizations (+45 and −45). The weighting at the other polarization(e.g. +45) is always 1.

In an alternative embodiment, if the UE is configured with an extensionof LC codebook CB4-2 (Codebook-Config 1 corresponds to Class A ran 7 W1and Codebook-Config 2, 3, 4 corresponds to Class A rank 1 W1) in whichfor L=2 and Codebook-Config=2, 3, or 4, the W2 codebook comprises of(hence is a union of two W2 codebooks) both single beam selection basedon legacy W2 (LTE Rel. 13 Class A codebook), which for rank 1corresponds to 1 out of 4 beam selection and 1 out of 4 co-phase {1, j,−1, j} selection, and rank 2 corresponds to 1 out of 4 beam selectionand 1 out of 2 co-phase pair {(1, −1), (j, −j)} selection; and two beamselection based on W2 codebook in LC codebook CB4-2 for L=2.

In another alternative embodiment, if the UE is configured with anextension of LC codebook CB4-2 (Codebook-Config 1 corresponds to Class Aran 7 W1 and Codebook-Config 2, 3, 4 corresponds to Class A rank 1 W1)in which for L=4 and Codebook-Config=2, 3, or 4, the W2 codebookcomprises of (hence is a union of two W2 codebooks) both single beamselection based on legacy W2 (LTE Rel. 13 Class A codebook), which forrank 1 corresponds to 1 out of 4 beam selection and 1 out of 4 co-phase{1, j, −1, j} selection, and rank 2 corresponds to 1 out of 4 beamselection and 1 out of 2 co-phase pair {(1, −1), (j, −j)} selection; andfour beam selection based on W2 codebook in LC codebook CB4-2 for L=4.

In another alternative embodiment, if the UE is configured with anextension of LC codebook CB2 (Codebook-Config 1 corresponds tounrestricted orthogonal W1 and Codebook-Config 2, 3, 4 corresponds toClass A rank 1 W1) in which for L=2 and Codebook-Config=2, 3, or 4, theW2 codebook comprises of (hence is a union of two W2 codebooks) bothsingle beam selection based on legacy W2 (LTE Rel. 13 Class A codebook),which for rank 1 corresponds to 1 out of 4 beam selection and 1 out of 4co-phase {1, j, −1, −j} selection, and rank 2 corresponds to 1 out of 4beam selection and 1 out of 2 co-phase pair {(1, −1), (j, −j)}selection; and two beam selection based on W2 codebook in LC codebookCB2 for L=2.

In another alternative embodiment, if the UE is configured with anextension of LC codebook CB2 (Codebook-Config 1 corresponds tounrestricted orthogonal W1 and Codebook-Config 2, 3, 4 corresponds toClass A rank 1 W1) in which for L=4 and Codebook-Config=2, 3, or 4, theW2 codebook comprises of (hence is a union of two W2 codebooks) bothsingle beam selection based on legacy W2 (LTE Rel. 13 Class A codebook),which for rank 1 corresponds to 1 out of 4 beam selection and 1 out of 4co-phase {1, j, −1, −j} selection, and rank 2 corresponds to 1 out of 4beam selection and 1 out of 2 co-phase pair {(1, −1), (j, −j)}selection; and four beam selection based on W2 codebook in LC codebookCB2 for L=4.

In another alternative embodiment, if the UE is configured with an LCcodebook which for rank 1 corresponds to the rank 1 LC codebook CB2(Codebook-Config 1 corresponds to unrestricted orthogonal basis), andrank 2 corresponds to the rank 2 LC codebook CB4-2 (Codebook-Config 1corresponds to Class A rank 7 orthogonal basis). Note that the rank 1and rank 2 LC codebooks for Codebook-Config 2, 3, 4 are the same in bothCB2 and CB4-2.

In one extension, if the UE is configured with L=2 andCodebook-Config=2, 3, or 4, then the W2 codebook comprises of (hence isa union of two W2 codebooks) both single beam selection based on legacyW2 (LTE Rel. 13 Class A codebook), which for rank 1 corresponds to 1 outof 4 beam selection and 1 out of 4 co-phase {1, j, −1, −j} selection,and rank 2 corresponds to 1 out of 4 beam selection and 1 out of 2co-phase pair {(1, −1), (j, −j)} selection; and two beam selection basedon W2 codebook in LC codebook CB2 or CB4-2 for L=2.

In another extension, if the UE is configured with L=4 andCodebook-Config=2, 3, or 4, then the W2 codebook comprises of (hence isa union of two W2 codebooks) both single beam selection based on legacyW2 (LTE Rel. 13 Class A codebook), which for rank 1 corresponds to 1 outof 4 beam selection and 1 out of 4 co-phase {1, j, −1, −j} selection,and rank 2 corresponds to 1 out of 4 beam selection and 1 out of 2co-phase pair {(1, −1), (j, −j)} selection; and four beam selectionbased on W2 codebook in LC codebook CB2 or CB4-2 for L=4.

In yet another extension, if the UE is configured with L=2 or 4 andCodebook-Config=2, 3, or 4, then the W2 codebook comprises of (hence isa union of two W2 codebooks) both single beam selection based on legacyW2 (LTE Rel. 13 Class A codebook), which for rank 1 corresponds to 1 outof 4 beam selection and 1 out of 4 co-phase {1, j, −1, −j} selection,and rank 2 corresponds to 1 out of 4 beam selection and 1 out of 2co-phase pair {(1, −1), (j, −j)} selection; and two or four beamselection based on W2 codebook in LC codebook CB2 or CB4-2 for L=2 or 4.

In another embodiment, the union of legacy (LTE Rel. 13 or 14 Class A)and LC W2 codebooks is always supported for one (e.g. L=2) or all Lvalues (e.g. L=2, 4) and for Codebook-Config 2, 3, 4, and the UE reportsone of the two types of W2 (or 2^(nd) PMI i₂) in the CSI report.

In yet another embodiment, whether to use legacy (LTE Rel. 13 or 14Class A) W2 or LC codebook W2 or their union is configurable viahigher-layer RRC signaling and the UE reports one of the three types ofW2 (2^(nd) PMI i₂) in the CSI report depending on the configuration.

In yet another embodiment, the UE reports both the W2 codebook (legacyor LC codebook) and the corresponding 2^(nd) PMI in the CSI report.

FIG. 28 illustrates an example LC codebook CB5 2800 according toembodiments of the present disclosure. An embodiment of the LC codebookCB5 2800 shown in FIG. 28 is for illustration only. One or more of thecomponents illustrated in FIG. 28 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, a UE is configured with a dual-stage or double LCcodebook: W=W1W2, referred to as CB5 as shown in FIG. 28, using RRCparameter Codebook-Config, where for Codebook-Config 1, W1 codebookcorresponds orthogonal W1 codebook based on Rel-13 Class A rank 7codebook for both rank 1 and 2 LC codebook, where orthogonal basis has 4fixed beams, which for 1D port layouts correspond to Class A rank 7 forCodebook-Config 4, i.e. (4,1) orthogonal, and 2D port layouts correspondto Class A rank 7 for Codebook-Config 2, i.e. (2,2) orthogonal;non-equal WB beam power using 2-bit per beam is used to combine 4 beams;and L out of 4 beams are selected WB.

In some embodiments, a UE is configured with a dual-stage or double LCcodebook: W=W1W2, referred to as CB5 as shown in FIG. 28, using RRCparameter Codebook-Config, where for Codebook-Config 2, W1 codebookcorresponds non-orthogonal W1 codebook based on Rel-13 Class A rank 1codebook for both rank 1 and 2 LC codebook, where non-orthogonal basishas 4 fixed beams, which for 1D port layouts correspond to Class A rank1 for Codebook-Config 4, i.e. (4,1) non-orthogonal, and 2D port layoutscorrespond to Class A rank 1 for Codebook-Config 2, i.e. (2,2)non-orthogonal; equal gain combining (so, WB beam power indication isneeded); and L out of 4 beams selected SB.

The W2 codebook is common to both Codebook-Configs and is according tosome embodiments of disclosure. Also, there are two alternatives for L:UE recommends a preferred L value; and L is configured via higher layerRRC signaling.

In some embodiments, a UE is configured with a dual-stage or double LCcodebook: W=W1W2, referred to as CB6, using RRC parameterCodebook-Config, where for rank 1, LC codebook CB2 proposed earlier inthe present disclosure is used; and for rank 2, LC codebook CB5 proposedearlier in the present disclosure is used.

In some embodiments, a UE is configured with a dual-stage or double LCcodebook: W=W1W2, referred to as CB6, using RRC parameterCodebook-Config, where for rank 1, LC codebook CB5 proposed earlier inthe present disclosure is used; and for rank 2, LC codebook CB2 proposedearlier in the present disclosure is used.

In some embodiments, a UE is configured with the LC codebook foradvanced CSI reporting using an RRC parameter advancedCodebookEnabledsuch that the RI reporting is according to one of the followingalternatives. In one example of RI=0 bit (no RI reporting), if UE isconfigured with advanced CSI reporting (i.e., advancedCodebookEnabled isturned ON), then there is no RI reporting, which the reported CSIcorresponds to rank 1 LC codebook proposed in disclosure (e.g. CB0-CB6),regardless of how many layers UE can support. In this case, the dynamicSU/MU switching is restricted to 1 layers. In another example of RI=1bit: if UE is configured with advanced CSI reporting (i.e.,advancedCodebookEnabled is turned ON), then RI reporting is always 1bit, regardless of how many layers UE can support. In this case, thedynamic SU/MU switching is restricted to 2 layers. The reported RIcorresponds to one of the following sub-alternatives: rank 1 and 2 LCcodebooks proposed in disclosure (e.g. CB0-CB6); and rank 1 is LCcodebook proposed in disclosure (e.g. CB0-CB6), and rank 2 is LTE Rel.13 (and 14) Class A codebook. In yet another example of RI=2 bits, if UEis configured with advanced CSI reporting (i.e., advancedCodebookEnabledis turned ON), then RI reporting is always 2 bit, regardless of how manylayers UE can support. In this case, the dynamic SU/MU switching isrestricted to 4 layers. The reported RI corresponds to one of thefollowing sub-alternatives: rank 1-4 LC codebooks where rank 1-2 are asproposed in disclosure (e.g. CB0-CB6); rank 1-2 is LC codebook proposedin disclosure (e.g. CB0-CB6), and rank 3-4 is LTE Rel. 13 (and 14) ClassA codebook; and rank 1 is LC codebook proposed in disclosure (e.g.CB0-CB6), and rank 2-4 is LTE Rel. 13 (and 14) Class A codebook. In yetanother example of RI=3 bits, if UE is configured with advanced CSIreporting (i.e., advancedCodebookEnabled is turned ON), then RIreporting is always 3 bit, regardless of how many layers UE can support.In this case, the dynamic SU/MU switching is restricted to 8 layers. Thereported RI corresponds to one of the following sub-alternatives: rank1-4 LC codebooks where rank 1-2 are as proposed in disclosure (e.g.CB0-CB6), and rank 3-8 is LTE Rel. 13 (and 14) Class A codebook; rank1-2 is LC codebook proposed in disclosure (e.g. CB0-CB6), and rank 3-8is LTE Rel. 13 (and 14) Class A codebook; and rank 1 is LC codebookproposed in disclosure (e.g. CB0-CB6), and rank 2-8 is LTE Rel. 13 (and14) Class A codebook.

In some embodiments, a UE is configured with an LC codebook W=W1W2 withL=2 beams for both rank 1 and rank 2, where W1 and W2 codebooks are usedto report WB and SB components of the PMI, respectively. The W1 codebookcomprises of the following components. In one example, uniformly spacedorthogonal beam groups of size (L₁, L₂) that are constructed as follows:for N₁N₂≤8, orthogonal beam group correspond to the full N₁×N₂orthogonal DFT basis, i.e. (L₁, L₂)=(N₁, N₂); and for N₁N₂>8, a group of8 uniformly spaced orthogonal beams are selected which corresponds toeither (L₁, L₂)=(4,2) if 2D antenna port layouts with N₁≥N₂ and N₂≠1;(L₁, L₂)=(2, 4) if 2D antenna port layouts with N₁<N₂ and N₂≠1; or (L₁,L₂)=(8,1) if 1D antenna port layouts with N₂=1. In another example ofbeam selection, L=2 beams are selected from L₁L₂ beams in the selectedorthogonal beam group. In yet another example of beam power, L=2selected beams are associated with beam power level using a 2-bit beampower codebook. Note that the power level of the stronger beam (beamwith larger power) can be assumed to be 1 without loss of generality.So, the power level of the 2^(nd) beam (beam with lower or equal powerlevel than the 1^(st) beam) need to be selected from the beam powercodebook.

The illustration of orthogonal beams in the proposed codebook is thesame as shown in FIG. 31 for Codebook-Config 1. The W2 codebookcomprising of the following components: L=2 beams are combined usingQPSK={1, j, −1, −j} phase codebook; and in case of rank 2, the phase tocombine two beams are selected independently for the two layers.

Mathematically, the structure of the proposed LC codebook is as follows.

${W_{1} = \begin{bmatrix}B & 0 \\0 & B\end{bmatrix}},{B = \left\lbrack {{p_{0}b_{k_{1}^{(0)},k_{2}^{(0)}}},{p_{1}b_{k_{1}^{(1)},k_{2}^{(1)}}}} \right\rbrack},{{{where}\mspace{14mu} {for}\mspace{14mu} {rank}\mspace{14mu} 1\text{:}\mspace{14mu} W} = {\begin{bmatrix}{\overset{\sim}{w}}_{0,0} \\{\overset{\sim}{w}}_{1,1}\end{bmatrix} = {W_{1}W_{2}}}},{and}$ ${W_{2} = \begin{bmatrix}c_{0,0} \\c_{1,0}\end{bmatrix}},{{{for}\mspace{14mu} {rank}\mspace{14mu} 2\text{:}\mspace{14mu} W} = {\begin{bmatrix}{\overset{\sim}{w}}_{0,0} & {\overset{\sim}{w}}_{0,1} \\{\overset{\sim}{w}}_{1,0} & {\overset{\sim}{w}}_{1,1}\end{bmatrix} = {W_{1}W_{2}}}},{and}$ ${W_{2} = \begin{bmatrix}c_{0,0} & c_{0,1} \\c_{1,0} & c_{1,1}\end{bmatrix}},{c_{r,l} = \left\lbrack {c_{r,l,0},c_{r,l,1}} \right\rbrack^{T}},{r = 0},1,{l = 0},{{{1{\overset{\sim}{w}}_{r,l}} = {\sum\limits_{i = 0}^{1}{b_{k_{1}^{(i)},k_{2}^{(i)}} \cdot p_{i} \cdot c_{r,l,i}}}};{r = 0}},1,{l = 0},1$

b_(k) ₁ _(,k) ₂ is a 2D DFT beam from the oversampled DFT beam grid,where k₁=0, 1, . . . N₁O₁−1, and k₂=0, 1, . . . N₂O₂−1. 0≤p_(i)≤1 beampower scaling factor for beam i. c_(r,l,i) beam combining coefficientfor beam i and on polarization r and layer l, where (O₁, O₂) is theoversampling factor in two dimensions. An example value for which is(O₁, O₂)=(4, 4) for 2D port layouts, and (4,1) for 1D port layouts.Another example is to use LTE Rel. 13 and LTE Rel. 14 (O₁, O₂) valuesfor different (N₁, N₂) values, where 2N₁N₂∈{4, 8, 12, 16, 20, 24, 28,32}. There are three alternatives for the supported values of (N₁, N₂).In one example of Alt 0, all possible (N₁, N₂) values are supported. Inanother example of Alt 1, all possible (N₁, N₂) values are supported for2D port layouts, and all (N₁, N₂) values are supported for 1D portlayouts with N₂=1. In yet another example of Alt 2, (N₁, N₂) valuessupported in LTE Rel. 13 and LTE Rel. 14 Class A codebook are supportedin the proposed LC codebook.

The leading beam index (k₁ ⁽⁰⁾,k₂ ⁽⁰⁾) is given by k₁ ⁽⁰⁾=0, 1, . . .N₁O₁−1 and k₂ ⁽⁰⁾=0, 1, . . . N₂O₂−1. The leading beam corresponds tothe strongest beam with beam power p₀=1. The second beam index (k₁ ⁽¹⁾,k₂ ⁽¹⁾) is given by k₁ ⁽¹⁾=k₁ ⁽⁰⁾+O₁d₁, and k₂ ⁽¹⁾=k₂ ⁽⁰⁾+O₂d₂, where(d₁, d₂) satisfies the following: d₁∈{0, 1, . . . , min(N₁,L₁)−1};d₂∈{0, 1, . . . , min(N₂,L₂)−1}; and (d₁, d₂)≠(0,0), where (L₁, L₂) isdefined above.

The beam power level for the two beams are as follows: p₀=1, p₁∈{1,√{square root over (0.5)}, √{square root over (0.25)}, 0}. The W2codebook for layer 1 and layer 2 is given by c_(0,0,0)=c_(0,1,0)=1; andc_(r,l,i)∈{1, j, −1, −j}, ∀i,r,l∈{0, 1}.

The W1 payload for N₁=N₂=O₁=O₂=4 can be decomposed as follows:indicating the leading beam with stronger power:┌log₂(N₁N₂O₁O₂)┐=┌log₂(16N₁N₂)┐=8 bits; indicating the second beam,which requires ┌log₂(₁ ⁷)┐=3 bits; and the power level of the 2^(nd)beam, which requires 2 bits. The W1 and W2 payload sizes is summarizedin Table 30.

TABLE 30 W1 and W2 payload Rank W1 (bits) W2 (bits) 1 13 6 2 13 12

The WB components of the codebook is reported jointly as the first PMIpair (i_(1,1), i_(1,2)). For example, the first PMI i_(1,1) jointlyindicates one of N₁O₁ states for the first index of the leading beam k₁⁽⁰⁾, one of 7 states for selecting the 2nd beam and one of 4 states forthe beam power level for the 2nd beams, which amounts to 7×4×N₁O₁ statesin total. If B=B1+B2+B3 is the total number of bits for this jointreporting, where B1, B2, and B3 are for the three WB components, i.e.i_(1,1)=0, 1, . . . , 2^(B)−1, and B1 corresponds to the leastsignificant bits (LSB) and B3 corresponds to the most signficant bits(MSB), then there may be following alternatives for this jointindication: B1=┌log₂ N₁O₁┐ for the first index of the leading beam k₁⁽⁰⁾, B2=2 for the power level of the 2nd beam, and B3=3 for selectingthe 2nd beam; B1=┌log₂ N₁O₁┐ for the first index of the leading beam k₁⁽⁰⁾, B3=2 for the power level of the 2nd beam, and B2=3 for selectingthe 2nd beam; B2=┌log₂ N₁O₁┐ for the first index of the leading beam k₁⁽⁰⁾, B1=2 for the power level of the 2nd beam, and B3=3 for selectingthe 2nd beam; B2=┌log₂ N₁O₁┐ for the first index of the leading beam k₁⁽⁰⁾, B3=2 for the power level of the 2nd beam, and B1=3 for selectingthe 2nd beam; B3=┌log₂ N₁O₁┐ for the first index of the leading beam k₁⁽⁰⁾, B1=2 for the power level of the 2nd beam, and B2=3 for selectingthe 2nd beam; and B3=┌log₂ N₁O₁┐ for the first index of the leading beamk₁ ⁽⁰⁾, B2=2 for the power level of the 2nd beam, and B1=3 for selectingthe 2nd beam. The 2nd PMI i_(1,2) indicates one of N₂O₂ states for thesecond index of the leading beam k₂ ⁽⁰⁾.

In a sub-embodiment of this embodiment, the second orthogonal beam index(d₁, d₂) relative to the leading beam index (k₁ ⁽⁰⁾, k₂ ⁽⁰⁾) issatisfies d₁=0, 1, . . . , L₁−1 and d₂=0, 1, . . . , L₂−1, where (L₁,L₂)is according to the following: N₁≥N₂>1:L₁=min(N₁,4), L₂=2; N₂>N>1:L₂=min(N₂,4), L₁=2; and N₂=1: L₁=min(N₁,8), L₂=1.

The detailed values of the second beam index (d₁,d₂) for differentantenna port layouts are tabulated in Table 31. The number of differentsecond beam indices is L₁,L₂−1 (note that (0, 0) is not included).Therefore, the number of bits to report the second beam index is ┌log₂(L₁L₂)┐ (if (0, 0) is also counted) or ┌log₂(L₁L₂−1)┐ (if (0, 0) is notcounted) if reported as one PMI and is ┌log₂ (L₁)┐ and ┌log₂ (L₂)┐ ifreported as two PMIs for the two dimension.

TABLE 31 Mapping between second beam index and (d₁, d₂) (d₁, d₂) Index 4ports (N₁ = 2, N₂ = 1) (1, 0) 0 8 ports (N₁ = 4, N₂ = 1) {(1, 0), (2,0), (3, 0)} 0-2 8 ports (N₁ = 2, N₂ = 2) {(1, 0), (0, 1), (1, 1)} 0-2 12ports (N₁ = 2, N₂ = 3) {(0, 1), (0, 2), (1, 0), (1, 1), (1, 2)} 0-4 12ports (N₁ = 3, N₂ = 2) {(1, 0), (2, 0), (0, 1), (1, 1), (2, 1)} 0-416/20/24/28/32 ports {(0, 1), (0, 2), (0, 3), (1, 0), 0-6 (N₂ > N₁ > 1)(1, 1), (1, 2), (1, 3)} 16/20/24/28/32 ports {(1, 0), (2, 0), (3, 0),(0, 1), 0-6 (N₁ ≥ N₂ > 1) (1, 1), (2, 1), (3, 1)} 16/20/24/28/32 ports{(1, 0), (2, 0), (3, 0), (4, 0), 0-6 (N₁ ≥ 8, N₂ = 1) (5, 0), (6, 0),(7, 0)}

In one embodiment 0, the UE is configured with an LC codebook where rank1 and rank 2 pre-coders are given according to at least one of thefollowing sub-embodiments. In sub-embodiment 0-1, the rank 1 and rank 2LC pre-coders are derived without beam selection and with differentco-phase for all beams, and are given by:

${W_{l,m,n,k}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}w_{l,m,n,k}^{( + )} \\w_{l,m,n,k}^{( - )}\end{bmatrix}}},{W_{l,m,n,k}^{(2)} = {\frac{1}{2}\begin{bmatrix}w_{l,m,k_{0}}^{( + )} & w_{l,m,k_{1}}^{( + )} \\w_{l,m,n_{0},k_{0}}^{( - )} & {- w_{l,m,n_{1},k_{1}}^{( - )}}\end{bmatrix}}}$${{Where}\mspace{20mu} w_{l,m,k}^{( + )}} = {\frac{x_{l,m}c_{k}}{{{x_{l,m}c_{k}} + {x_{l,m}\varphi_{n}c_{k}}}}\mspace{14mu} {and}}$${w_{l,m,n,k}^{( - )} = \frac{x_{l,m}\varphi_{n}c_{k}}{{{x_{l,m}c_{k}} + {x_{l,m}\varphi_{n}c_{k}}}}}\;$

for rank 1;

$w_{l,m,k_{r}}^{( + )} = {\frac{x_{l,m}c_{k_{r}}}{{{x_{l,m}c_{k_{r}}} + {x_{l,m}\varphi_{n_{r}}c_{k_{r}}}}}\mspace{14mu} {and}}$${w_{l,m,n_{r},k_{r}}^{( - )} = \frac{x_{l,m}\varphi_{n}c_{k}}{{{x_{l,m}c_{k_{r}}} + {x_{l,m}\varphi_{n_{r}}c_{k_{r}}}}}}\;$

for layer r=0, 1 of rank 2; n=[n₀ n₁] and k=[k₀ k₁] respectively areco-phase pair and coefficient pair indices for rank 2; x_(l,m) is a beamgroup (comprising of L beams), selected from a codebook, an example ofwhich are Table 30 (non-orthogonal basis) and Table 31 (orthogonalbasis) for L=4; ϕ_(n)=diag(φ_(n,0) φ_(n,1) . . . φ_(n,L−1)) is adiagonal matrix with co-phase values φ_(n,0), φ_(n,1), . . . , φ_(n,L−1)at the diagonal entries that are selected from a co-phase codebookproposed earlier in the present disclosure. For rank 2, ϕ_(n), wherer=0, 1 is defined similarly.

In sub-embodiment 0-2, the rank 1 and rank 2 LC pre-coders are derivedwith B out of L beam selection, where 1≤B≤L, and with different co-phasefor all beams, and are given by:

${W_{l,m,b,n,k}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}w_{l,m,b,k}^{( + )} \\w_{l,m,b,n,k}^{( - )}\end{bmatrix}}},{W_{l,m,b,n,k}^{(2)} = {\frac{1}{2}\begin{bmatrix}w_{l,m,b,k_{0}}^{( + )} & w_{l,m,b,k_{1}}^{( + )} \\w_{l,m,b,n_{0},k_{0}}^{( - )} & {- w_{l,m,b,n_{1},k_{1}}^{( - )}}\end{bmatrix}}}$${{Where}\mspace{20mu} w_{l,m,b,k}^{( + )}} = {\frac{x_{l,m}E_{B,b}c_{k}}{{{x_{l,m}c_{k}} + {x_{l,m}E_{B,b}\varphi_{n}c_{k}}}}\mspace{14mu} {and}}$${w_{l,m,b,n,k}^{( - )} = \frac{x_{l,m}E_{B,b}\varphi_{n}c_{k}}{{{x_{l,m}c_{k}} + {x_{l,m}E_{B,b}\varphi_{n}c_{k}}}}}\;$

for rank 1;

$w_{l,m,b,k_{r}}^{( + )} = {\frac{x_{l,m}E_{B,b}c_{k_{r}}}{{{x_{l,m}c_{k_{r}}} + {x_{l,m}E_{B,b}\varphi_{n_{r}}c_{k_{r}}}}}\mspace{14mu} {and}}$$w_{l,m,b,n_{r},k_{r}}^{( - )} = \frac{x_{l,m}E_{B,b}\varphi_{n_{r}}c_{k_{r}}}{{{x_{l,m}c_{k_{r}}} + {x_{l,m}E_{B,b}\varphi_{n_{r}}c_{k_{r}}}}}$

for layer r=0, 1 of rank 2; n=[n₀ n₁] and k=[k₀ k₁] respectively areco-phase pair and coefficient pair indices for rank 2; x_(l,m) is a beamgroup (comprising of L beams), selected from a codebook, an example ofwhich are Table 30 (non-orthogonal basis) and Table 31 (orthogonalbasis) for L=4; E_(B,b) is the beam selection matrix, an example ofwhich is Table 31 for L=4; ϕ_(n)=diag(φ_(n,0) φ_(n,1) . . . φ_(n,L−1))is a diagonal matrix with co-phase values φ_(n,0), φ_(n,1), . . . ,φ_(n,L−1) at the diagonal entries that are selected from a co-phasecodebook proposed earlier in the present disclosure. For rank 2, φ_(n),where r=0, 1 is defined similarly.

c_(k)=[c_(k,0) c_(k,1) . . . c_(k,L−1)]^(T) is a length-L coefficientvector, selected from a coefficient codebook proposed earlier in thepresent disclosure. For rank 2, c_(k) where r=0, 1 is defined similarly.

According to Alt 0 in FIG. 14, the pre-coder for layer r=0, 1, . . . ,R−1 of the rank-R LC codebook is given by

$p^{(r)} = {{Bc} = {{\begin{bmatrix}{b_{0}b_{1}\ldots \; b_{L - 1}} & {0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{14mu} 0} \\{0\mspace{14mu} 0\mspace{14mu} \ldots \mspace{11mu} 0} & {b_{0}b_{1}\; \ldots \; b_{L - 1}}\end{bmatrix}\begin{bmatrix}1 \\c_{1}^{(r)} \\\vdots \\c_{{2L} - 1}^{(r)}\end{bmatrix}}.}}$

If c_(l) ^((r)) belongs to QPSK alphabet {1, −1, j, −j}, then the numberof bits to report rank-R LC coefficients (i.e. 2^(nd) PMI reportingoverhead associated with W₂ codebook) is r×4^(2L−1). This implies thatfor rank-2 (i.e. R=2), the 2^(nd) PMI reporting overhead is doubled whencompared with that for rank-1. This increase in PMI reporting overheadmay be an issue if 2^(nd) PMI has to be reported periodically usingPUCCH because the limited number of CSI bits that can be reported usingPUCCH Format 2 or 3, for example. It is therefore desired to designhigher rank LC codebooks (e.g. rank 2) with PMI reporting overheadcomparable to that for rank 1. An example of such reduced overheadrank-2 LC codebook is proposed below based on Alt 1 in FIG. 14, whereco-phase for the two polarizations and LC coefficients are separated,hence can be quantized using respective codebooks.

In some embodiments, a UE is configured with a dual-stage LC codebookW=W₁W₂, according to some embodiments to the present disclosure, inwhich the layer r=0, 1, . . . , R−1 of the second stage rank-R W₂codebook has pre-coders for linear combination of L W₁ beams with thefollowing structure:

${a^{(r)} = {{\begin{bmatrix}e_{0} & e_{1} & \ldots & e_{L - 1} \\{\varphi_{0}^{(r)}e_{0}} & {\varphi_{1}^{(r)}e_{1}} & \ldots & {\varphi_{L - 1}^{(r)}e_{L - 1}}\end{bmatrix}\begin{bmatrix}1 \\c_{1}^{(r)} \\\vdots \\c_{L - 1}^{(r)}\end{bmatrix}} = \left\lbrack {1\mspace{14mu} c_{1}^{(r)}\mspace{14mu} \ldots \mspace{14mu} c_{L - 1}^{(r)}\mspace{14mu} \varphi_{0}^{(r)}\mspace{11mu} \varphi_{1}^{(r)}\mspace{14mu} c_{1}^{(r)}\mspace{14mu} \ldots \mspace{14mu} \varphi_{L - 1}^{(r)}c_{L - 1}^{(r)}} \right\rbrack^{T}}},$

where ϕ^((r)): [ϕ₀ ^((r)) ϕ₁ ^((r)) . . . ϕ_(L−1) ^((r))] corresponds tothe co-phase component of the W₂ codebook; and c^((r))=[1 c₁ ^((r)) . .. c_(L−1) ^((r))] corresponds to the coefficient component of the W₂codebook.

Note that the coefficient for the 1^(st) beam can be assumed to be 1,i.e., c₀ ^((r))=1, for all layers r. For L=2, the rank 2 W₂ pre-coder isthen given by

$\begin{bmatrix}a^{(0)} \\a^{(1)}\end{bmatrix} = {\begin{bmatrix}1 & c_{1}^{(0)} & \varphi_{0}^{(0)} & \varphi_{0}^{(0)} & c_{1}^{(0)} \\1 & c_{1}^{(1)} & \varphi_{0}^{(1)} & \varphi_{0}^{(1)} & c_{1}^{1}\end{bmatrix}^{T}.}$

For L=4, the rank 2 pre-coder is given by

$\begin{bmatrix}a^{(0)} \\a^{(1)}\end{bmatrix} = {\begin{bmatrix}1 & c_{1}^{(0)} & c_{2}^{(0)} & c_{3}^{(0)} & \varphi_{0}^{(0)} & {\varphi_{1}^{(0)}c_{1}^{(0)}} & {\varphi_{2}^{(0)}c_{2}^{(0)}} & {\varphi_{3}^{(1)}c_{3}^{(1)}} \\1 & c_{1}^{(1)} & c_{2}^{(1)} & c_{3}^{(1)} & \varphi_{0}^{(1)} & {\varphi_{1}^{(1)}c_{1}^{(1)}} & {\varphi_{2}^{(1)}c_{2}^{(1)}} & {\varphi_{3}^{(1)}c_{3}^{(1)}}\end{bmatrix}^{T}.}$

Let W and W be the rank-2 codebooks for the co-phase component

$\begin{bmatrix}\varphi^{(0)} \\\varphi^{(1)}\end{bmatrix} = \begin{bmatrix}\varphi_{0}^{(0)} & \varphi_{1}^{(0)} & \ldots & {\; \varphi_{L - 1}^{(0)}} \\\varphi_{0}^{(1)} & \varphi_{1}^{(1)} & \ldots & {\; \varphi_{L - 1}^{(1)}}\end{bmatrix}^{T}$

and the coefficient component

$\begin{bmatrix}c^{(0)} \\c^{(1)}\end{bmatrix} = \begin{bmatrix}1 & c_{1}^{(0)} & \ldots & {\; c_{L - 1}^{(0)}} \\1 & c_{1}^{(1)} & \ldots & {\; c_{L - 1}^{(1)}}\end{bmatrix}^{T}$

for the two layers, respectively.

In some embodiments, the rank-2 W_(coph) ⁽²⁾ codebook is according toone or a combination of the following alternatives. In one example ofAlt A for a given beam l∈{(0, 1, . . . , L−1}, the same co-phase is usedfor the two layers, i.e., ϕ_(l) ⁽⁰⁾=ϕ_(l) ⁽¹⁾∈{1,j, −1, −j}, forexample. So, the total number co-phase pair combinations for L beams is4^(L). In another example of Alt B for a given beam l∈{(0, 1, . . . ,L−1}, the co-phase pair for the two layers [ϕ_(l) ⁽⁰⁾ ϕ_(l) ⁽¹⁾] belongsto {[1 −1], [j −j]}. Note that these are the two co-phase pairs in theLTE Rel. 13 Class A rank-2 codebook. So, the total number co-phase paircombinations for L beams is 2^(L). In yet another example of Alt C foreach beam l∈{(0, 1, . . . , L−1} and for each layer rε{0,1}, theco-phase ϕ_(l) ^((r)) belongs to {1, −1}. So, the total number co-phasepair combinations for L beams is 2^(L)×2^(L). In yet another example ofAlt D for each beam l∈{0, 1, . . . , L−1}, the co-phase pair for the twolayers [ϕ_(l) ⁽⁰⁾ ϕ_(l) ⁽¹⁾] belongs to {[1 −1], [j −j], [−1 1], [−jj]}. So, the total number co-phase pair combinations for L beams is4^(L). In yet another example of Alt E for each beam l∈{0, 1, . . . ,L−1} and for each layer r∈{0,1}, the co-phase ϕ_(l) ^((r)) belongs to{1, j, −1, −j}. So, the total number co-phase pair combinations for Lbeams is 4^(L)×4^(L). In yet another example of Alt F, the W_(coph) ⁽²⁾codebook is determined based on a condition such as one of thefollowing. In one instance of Orthogonality condition, (ϕ⁽⁰⁾)^(H)ϕ⁽¹⁾=0,which ensures that the co-phase values for the two layers that areapplied at the 2^(nd) antenna polarization are orthogonal. Note the1^(st) antenna polarization has a fixed co-phase equal to 1. In anotherinstance of identity condition, (ϕ_((l)) ⁽⁰⁾)^(H)ϕ_((l)) ⁽¹⁾=−1, whichensures that the correlation between two layers for the 2^(nd) antennapolarization cancels that for the 1^(st) antenna polarization (whoseco-phase is fixed to 1). Note that this identity condition guaranteesthat(α⁽⁰⁾)^(H)α⁽¹⁾=(c⁽⁰⁾)^(H)c⁽¹⁾+(c⁽⁰⁾)^(H)(ϕ⁽⁰⁾)^(H)ϕ⁽¹⁾c⁽¹⁾=(c⁽⁰⁾)^(H)c⁽¹⁾−(c⁽⁰⁾)^(H)c⁽¹⁾=0regardless of coefficients for two layers c⁽⁰⁾ and c⁽¹⁾. In yet anotherexample of Alt G, a combination of Alt A-Alt F is considered.

The co-phase codebook W_(coph) ⁽²⁾ alternatives A-E are summarized inTable 32. Note that the number of co-phase pair combinations for rank 1codebook is 4^(L) assuming QPSK {1, j, −1, −j} co-phase alphabet. So,Alt A-D ensures that the size of co-phase codebook for rank 2 is at mostequal to that for rank 1.

TABLE 32 Rank 2 co-phase codebook W_(coph) ⁽²⁾ alternatives Number ofco-phase pair Rank-2 co-phase for two layers combinations Alternative[ϕ_(l) ⁽⁰⁾ ϕ_(l) ⁽¹⁾] (2^(nd) antenna polarization) for L beams A ϕ_(l)⁽⁰⁾ = ϕ_(l) ⁽¹⁾ ϵ {1, j, −1, −j} 4^(L) B [ϕ_(l) ⁽⁰⁾ ϕ_(l) ⁽¹⁾] ϵ {[1−1], [j −j]} 2^(L) C ϕ_(l) ⁽⁰⁾, ϕ_(l) ⁽¹⁾ ϵ {1, −1} 2^(L) × 2^(L) =4^(L) D [ϕ_(l) ⁽⁰⁾ ϕ_(l) ⁽¹⁾] ϵ {[1 −1], [j −j], [−1 1], [−j j]} 4^(L) Eϕ_(l) ⁽⁰⁾, ϕ_(l) ⁽¹⁾ ϵ {1, j, −1, −j} 4^(L) × 4^(L)

In some embodiments, the rank-2 W_(coph) ⁽²⁾ codebook alternatives (AltA-Alt G) depends on the number of beams (L value). For example, if L=2,the rank-2 W_(coph) ⁽²⁾ codebook is according to one of Alt A or D or E,and if L=4, then the rank-2 W_(coph) ⁽²⁾ codebook is according to one ofAlt A-D.

In some embodiments, the rank-2 W_(coef) ⁽²⁾ codebook is according toone or a combination of the following alternatives. In one alternativeof Alt H for a given beam l∈{1, . . . , L−1}, the same coefficient isused for the two layers, i.e., c_(l) ⁽⁰⁾=c_(l) ⁽¹⁾∈{1, j, −1, −j}, forexample. So, the total number coefficient pair combinations for L beamsis 4^(L−1). In another alternative of Alt I for a given beam l∈{1, . . ., L−1}, the coefficient pair for the two layers [c_(l) ⁽⁰⁾ c_(l) ⁽¹⁾]belongs to {[1 −1], [j −j]}. So, the total number coefficient paircombinations for L beams is 2^(L−1). In yet another alternative of Alt Jfor each beam l∈{1, . . . , L−1} and for each layer r∈{0,1}, thecoefficient c_(l) ^((r)) belongs to {1, −1}. So, the total numbercoefficient pair combinations for L beams is 2^(L−1)×2^(L−1). In yetanother alternative of Alt K for each beam l∈{1, . . . , L−1}, thecoefficient pair for the two layers [c_(l) ⁽⁰⁾ c_(l) ⁽¹⁾] belongs to {[1−1], [j −j], [−1 1], [−j j]}. So, the total number coefficient paircombinations for L beams is 4^(L−1). In yet another alternative of Alt Lfor each beam l∈{1, . . . , L−1} and for each layer r∈{0,1}, thecoefficient c_(l) ^((r)) belongs to {1,j,−1,−j}. So, the total numbercoefficient pair combinations for L beams is 4^(L−1)×4^(L−1). In yetanother alternative of Alt M), the W_(coef) ⁽²⁾ codebook is determinedbased on a condition such as one of the following. In one instance oforthogonality condition, (c⁽⁰⁾)^(H)c⁽¹⁾=0, which ensures that thecoefficients for the two layers are orthogonal. In yet another instanceof Alt N, a combination of Alt H-Alt M may be considered.

TABLE 33 Rank 2 coefficient codebook W_(coef) ⁽²⁾ alternatives Number ofcoefficient pair Rank-2 coefficient for two layers combinationsAlternative [c_(l) ⁽⁰⁾ c_(l) ⁽¹⁾] (2^(nd) antenna polarization) for Lbeams H c_(l) ⁽⁰⁾ = c_(l) ⁽¹⁾ ϵ {1, j, −1, −j} 4^(L−1) I [c_(l) ⁽⁰⁾c_(l) ⁽¹⁾] ϵ {[1 −1], [j −j]} 2^(L−1) J c_(l) ⁽⁰⁾, c_(l) ⁽¹⁾ ϵ {1, −1}2^(L−1) × 2^(L−1) = 4^(L−1) K [c_(l) ⁽⁰⁾ c_(l) ⁽¹⁾] ϵ {[1 −1], [j −j],[−1 1], [−j j]} 4^(L−1) L c_(l) ⁽⁰⁾, c_(l) ⁽¹⁾ ϵ {1, j, −1, −j} 4^(L−1)× 4^(L−1)

In some embodiments, the rank-2 W_(coef) ⁽²⁾ codebook alternatives (AltH-Alt N) depends on the number of beams (L value). For example, if L=2,the rank-2 W_(coef) ⁽²⁾ codebook is according to one of Alt H or K or L,and if L=4, then the rank-2 W_(coef) ⁽²⁾ codebook is according to one ofAlt H-K.

In some embodiments, a UE is configured with the LC codebook accordingto some embodiments of the present disclosure in which the co-phase(derived from codebook W_(coph) ⁽²⁾ for 2^(nd) polarization) for eachlayer r in {0, 1, . . . , R−1} of the rank-R LC codebook is differentfor each of R layers, but LC coefficients (derived from codebookW_(coef) ⁽²⁾) for each of R layers is the same. In this case, theoverhead associated with the LC coefficient reporting does not increaseas the rank increases, and hence stays the same for all rank. Theoverhead associated with the co-phase (2^(nd) polarization) for L beamscan be according to one or a combination of the straightforwardextensions of Alt A-L in Table 32 and Table 33 for higher rank (R>2).

In some embodiments, a UE is configured with a dual-stage LC codebookW=W₁W₂, according to some embodiments of the present disclosure, inwhich the number of beams (i.e. L value) for linear combination dependson the rank of codebook. In one alternative, L>1 for rank 1 and 2, andL=1 for rank 3-8. Therefore, the proposed LC codebook is used to reportrank 1 and 2 CSI, and LTE Rel. 13 Class A or an extension of LTE Rel. 14is used to report rank 3-8 CSI. A few examples of this alternative is asfollows. In one example 0, L=4 for rank 1 and 2; and L=1 for rank 3-8(Class A codebook). In another example 1, L=4 for rank 1; L=2 out of 4per SB beam selection for rank 2; and L=1 for rank 3-8 (Class Acodebook). In another example 2, L=2 out of 4 per SB beam selection forrank 1 and 2; and L=1 for rank 3-8 (Class A codebook).

In another alternative, L>1 for rank 1-4, and L=1 for rank 5-8.Therefore, the proposed LC codebook is used to report rank 1-4 CSI, andLTE Rel. 13 Class A or an extension of LTE Rel. 14 is used to reportrank 3-8 CSI. A few examples of this alternative is as follows. In oneexample 3, L=4 for rank 1-4; and L=1 for rank 5-8 (Class A codebook). Inanother example 4, L=4 for rank 1-2; L=2 out of 4 per SB beam selectionfor rank 3-4; and L=1 for rank 5-8 (Class A codebook). In yet anotherexample 5, L=4 for rank 1; L=2 out of 4 per SB beam selection for rank2-4; and L=1 for rank 5-8 (Class A codebook). In yet another example 6,L=2 out of 4 per SB beam selection for rank 1-4; and L=1 for rank 5-8(Class A codebook). In yet another alternative, for a given rank 1-8, acombination of the above two alternatives or Examples 0-6 is used toconfigure the LC codebook.

In some embodiments, a UE is configured with a dual-stage LC codebookW=W₁W₂, according to some embodiments of the present disclosure, inwhich W₁ beam groups for each layer r in {0, 1, . . . , R−1} of therank-R LC codebook are according to one of the following alternatives.In one alternative of common W₁ beam group for R layers, an example ofwhich is orthogonal (DFT) beam group such as LTE Rel. 13 Class A rank7-8 W₁. In another alternative of different W₁ beam group for R layers,an example of which is as follows: LTE Rel. 13 Class A rank 1 W₁ for LCrank 1 W₁; LTE Rel. 13 Class A rank 3 W₁ for LC rank 2 W₁; LTE Rel. 13Class A rank 5 W₁ for LC rank 3 W₁; and LTE Rel. 13 Class A rank 7 W₁for LC rank 4 W₁.

In some embodiments, a UE is configured with the LC codebook accordingto some embodiments of the present disclosure in which Codebook-Configfor beam group type configuration (e.g., FIGS. 23-26) for rank-R LCcodebook is according to one of the following alternatives: commonCodebook-Config for all rank, for example Codebook-Config=2 and 4 forall rank; and different Codebook-Config for some or all ranks, forexample Codebook-Config=2, 3, and 4 for rank 1-2, and Codebook-Config=2and 4 for rank>2.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

None of the description in this application should be read as implyingthat any particular element, step, or function is an essential elementthat must be included in the claims scope. The scope of patented subjectmatter is defined only by the claims. Moreover, none of the claims areintended to invoke 35 U.S.C. § 112(f) unless the exact words “means for”are followed by a participle.

What is claimed is:
 1. A user equipment (UE) for a channel stateinformation (CSI) feedback in an advanced communication system, the UEcomprising: a transceiver configured to receive, from a base station(BS), CSI feedback configuration information for precoding matrixindicator (PMI) feedback based on a linear combination (LC) codebook,wherein the PMI feedback comprises a first PMI value (i₁) and a secondPMI value (i₂); and at least one processor configured to determine thefirst PMI value (i₁) and the second PMI value (i₂) indicating an LCprecoder that corresponds to a weighted linear combination of aplurality of beams, wherein: the plurality of beams are indicated byfirst beam information and second beam information, the first beaminformation indicating a reference beam in first and second dimensions,the second beam information indicating a distance from the referencebeam in the first and second dimensions, and the second PMI value (i₂)indicates a phase of weights assigned to the plurality of beams; andwherein the transceiver is further configured to transmit, to the BS,the CSI feedback over an uplink channel including the determined firstPMI value (i₁) and the determined second PMI value (i₂).
 2. The UE ofclaim 1, wherein CSI feedback further includes a power indicatorindicating a power of a weight assigned to the plurality of beams. 3.The UE of claim 2, wherein the power indicator is set to a value among afirst set of values comprising {0, √{square root over (¼)}, √{squareroot over (½)}, 1}.
 4. The UE of claim 1, wherein each beam of pluralityof beams corresponds to a discrete Fourier transform (DFT) beam selectedfrom an oversampled DFT codebook comprising DFT beams:${v_{l_{1},l_{2}} = \left\lbrack {u_{l_{2}}\mspace{20mu} e^{j\frac{2\pi \; l_{1}}{O_{1}N_{1}}}u_{l_{2}}\mspace{14mu} \ldots \mspace{20mu} e^{j\frac{2\pi \; {l_{1}{({N_{1} - 1})}}}{O_{1}N_{1}}}u_{l_{2}}} \right\rbrack^{T}},{{u_{l_{2}} = {{1\mspace{14mu} {if}\mspace{14mu} N_{2}} = 1}};}$$u_{l_{2}} = \left\lbrack {1\mspace{20mu} e^{j\frac{2\pi \; l_{2}}{O_{2}N_{2}}}\mspace{14mu} \ldots \mspace{20mu} e^{j\frac{2\pi \; {l_{2}{({N_{2} - 1})}}}{O_{2}N_{2}}}} \right\rbrack$otherwise, 0≤l₁≤O₁N₁−1, and 0≤l₂≤O₂N₂−1, where N₁ and N₂ indicate afirst and a second number of antenna ports in the first and the seconddimensions, respectively, and O₁ and O₂ indicate a first and a secondoversampling factors in the first and second dimensions, respectively.5. The UE of claim 1, wherein the plurality of beams comprise a firstbeam and a second beam.
 6. A base station (BS) for a channel stateinformation (CSI) feedback in an advanced communication system, the BScomprising: a transceiver configured to: transmit, to a user equipment(UE), CSI feedback configuration information for precoding matrixindicator (PMI) feedback based on a linear combination (LC) codebook,wherein the PMI feedback comprises a first PMI value (i₁) and a secondPMI value (i₂), wherein: the first PMI value (i₁) and the second PMIvalue (i₂) indicate an LC precoder that corresponds to a weighted linearcombination of a plurality of beams, the plurality of beams areindicated by first beam information and second beam information, thefirst beam information indicating a reference beam in first and seconddimensions, the second beam information indicating a distance from thereference beam in the first and second dimensions, and the second PMIvalue (i₂) indicates a phase of weights assigned to the plurality ofbeams; and receive, from the UE, the CSI feedback over an uplink channelincluding the first PMI value (i₁) and the second PMI value (i₂).
 7. TheBS of claim 6, wherein CSI feedback further includes a power indicatorindicating a power of a weight assigned to the plurality of beams. 8.The BS of claim 7, wherein the power indicator is set to a value among afirst set of values comprising {0, √{square root over (¼)}, √{squareroot over (½)}, 1}.
 9. The BS of claim 6, wherein each beam of pluralityof beams corresponds to a discrete Fourier transform (DFT) beam selectedfrom an oversampled DFT codebook comprising DFT beams:${v_{l_{1},l_{2}} = \left\lbrack {u_{l_{2}}\mspace{20mu} e^{j\frac{2\pi \; l_{1}}{O_{1}N_{1}}}u_{l_{2}}\mspace{14mu} \ldots \mspace{20mu} e^{j\frac{2\pi \; {l_{1}{({N_{1} - 1})}}}{O_{1}N_{1}}}u_{l_{2}}} \right\rbrack^{T}},{{u_{l_{2}} = {{1\mspace{14mu} {if}\mspace{14mu} N_{2}} = 1}};}$$u_{l_{2}} = \left\lbrack {1\mspace{20mu} e^{j\frac{2\pi \; l_{2}}{O_{2}N_{2}}}\mspace{14mu} \ldots \mspace{20mu} e^{j\frac{2\pi \; {l_{2}{({N_{2} - 1})}}}{O_{2}N_{2}}}} \right\rbrack$otherwise, 0≤l₁≤O₁N₁−1, and 0≤l₂≤O₂N₂−1, where N₁ and N₂ indicate afirst and a second number of antenna ports in the first and the seconddimensions, respectively, and O₁ and O₂ indicate a first and a secondoversampling factors in the first and second dimensions, respectively.10. The BS of claim 6, wherein the plurality of beams comprise a firstbeam and a second beam.
 11. A method of a user equipment (UE) for achannel state information (CSI) feedback in an advanced communicationsystem, the method comprising: receiving, from a base station (BS), CSIfeedback configuration information for precoding matrix indicator (PMI)feedback based on a linear combination (LC) codebook, wherein the PMIfeedback comprises a first PMI value (i₁) and a second PMI value (i₂);determining the first PMI value (i₁) and the second PMI value (i₂)indicating an LC precoder that corresponds to a weighted linearcombination of a plurality of beams, wherein: the plurality of beams areindicated by first beam information and second beam information, thefirst beam information indicating a reference beam in first and seconddimensions, the second beam information indicating a distance from thereference beam in the first and second dimensions, and the second PMIvalue (i₂) indicates a phase of weights assigned to the plurality ofbeams; and transmitting, to the BS, the CSI feedback over an uplinkchannel including the determined first PMI value (i₁) and the determinedsecond PMI value (i₂).
 12. The method of claim 11, wherein CSI feedbackfurther includes a power indicator indicating a power of a weightassigned to the plurality of beams.
 13. The method of claim 12, whereinthe power indicator is set to a value among a first set comprising {0,√{square root over (¼)}, √{square root over (½)}, 1}.
 14. The method ofclaim 11, wherein each beam of plurality of beams corresponds to adiscrete Fourier transform (DFT) beam selected from an oversampled DFTcodebook comprising DFT beams:${v_{l_{1},l_{2}} = \left\lbrack {u_{l_{2}}\mspace{20mu} e^{j\frac{2\pi \; l_{1}}{O_{1}N_{1}}}u_{l_{2}}\mspace{14mu} \ldots \mspace{20mu} e^{j\frac{2\pi \; {l_{1}{({N_{1} - 1})}}}{O_{1}N_{1}}}u_{l_{2}}} \right\rbrack^{T}},{{u_{l_{2}} = {{1\mspace{14mu} {if}\mspace{14mu} N_{2}} = 1}};}$$u_{l_{2}} = \left\lbrack {1\mspace{20mu} e^{j\frac{2\pi \; l_{2}}{O_{2}N_{2}}}\mspace{14mu} \ldots \mspace{20mu} e^{j\frac{2\pi \; {l_{2}{({N_{2} - 1})}}}{O_{2}N_{2}}}} \right\rbrack$otherwise, 0≤l₁≤O₁N₁−1, and 0≤l₂≤O₂N₂−1, where N₁ and N₂ indicate afirst and a second number of antenna ports in the first and the seconddimensions, respectively, and O₁ and O₂ indicate a first and a secondoversampling factors in the first and second dimensions, respectively.15. The method of claim 11, wherein the plurality of beams comprise afirst beam and a second beam.